value-schema

simple, easy-to-use, and declarative input validator

supports Node.js, TypeScript, Deno, and Bun

WARNING: Deno>=1.20 is NOT supported in v3, and is going to be supported in v4!

Introduction
Install
Loading
Reference
- types and constants
- basic usage
- boolean
- number
- string
- numeric string
- email
- enumeration
- array
- object
Changelog

Introduction

All of web applications need handling input parameters, consists of following steps:

existence check
- all required parameters exist?
- fill omittable parameters with default values
type check
- e.g., typeof age === "number"
- cast them if needed; "20"(string) to 20(number)
domain check
- e.g., 1 <= limit && limit <= 100
- revise them if needed; 0 to 1

value-schema does all of them, by compact and highly readable code!

example

import vs from "value-schema";

const schemaObject = { // schema for input
    id: vs.number({ // number, >=1
        minValue: 1,
    }),
    name: vs.string({ // string, max 16 characters (trims if over)
        maxLength: {
            length: 16,
            trims: true,
        },
    }),
    age: vs.number({ // number, integer (rounds down toward zero), >=0
        integer: vs.NUMBER.INTEGER.FLOOR_RZ,
        minValue: 0,
    }),
    email: vs.email(), // email
    state: vs.string({ // string, accepts only "active" and "inactive"
        only: ["active", "inactive"],
    }),
    classes: vs.array({ // array of number, separated by ",", ignores errors
        separatedBy: ",",
        each: {
            schema: vs.number(),
            ignoresErrors: true,
        },
    }),
    skills: vs.array({ // array of string, separated by ",", ignores errors
        separatedBy: ",",
        each: {
            schema: vs.string(),
            ignoresErrors: true,
        },
    }),
    creditCard: vs.numericString({ // numeric string, separated by "-", checks by Luhn algorithm
        separatedBy: "-",
        checksum: vs.NUMERIC_STRING.CHECKSUM_ALGORITHM.CREDIT_CARD,
    }),
    remoteAddr: vs.string({ // IPv4
        pattern: vs.STRING.PATTERN.IPV4,
    }),
    remoteAddrIpv6: vs.string({ // IPv6
        pattern: vs.STRING.PATTERN.IPV6,
    }),
    limit: vs.number({ // number, integer, omittable (sets 10 if omitted), >=1 (sets 1 if less), <=100 (sets 100 if greater)
        ifUndefined: 10,
        integer: true,
        minValue: {
            value: 1,
            adjusts: true,
        },
        maxValue: {
            value: 100,
            adjusts: true,
        },
    }),
    offset: vs.number({ // number, integer, omittable (sets 0 if omitted), >=0 (sets 0 if less)
        ifUndefined: 0,
        integer: true,
        minValue: {
            value: 0,
            adjusts: true,
        },
    }),
};
const input = { // input values
    id: "1",
    name: "Pablo Diego José Francisco de Paula Juan Nepomuceno María de los Remedios Ciprin Cipriano de la Santísima Trinidad Ruiz y Picasso",
    age: 20.5,
    email: "picasso@example.com",
    state: "active",
    classes: "1,3,abc,4",
    skills: "c,c++,javascript,python,,swift,kotlin",
    creditCard: "4111-1111-1111-1111",
    remoteAddr: "127.0.0.1",
    remoteAddrIpv6: "::1",
    limit: "0",
};
const expected = { // should be converted to this
    id: 1,
    name: "Pablo Diego José",
    age: 20,
    email: "picasso@example.com",
    state: "active",
    classes: [1, 3, 4],
    skills: ["c", "c++", "javascript", "python", "swift", "kotlin"],
    creditCard: "4111111111111111",
    remoteAddr: "127.0.0.1",
    remoteAddrIpv6: "::1",
    limit: 1,
    offset: 0,
};

// Let's apply!
const actual = vs.applySchemaObject(schemaObject, input);

// verification
assert.deepStrictEqual(actual, expected);

That's all! No control flows! Isn't it cool?

For details, see basic usage.

Install

install from npm registry.

npm install -S value-schema

Loading

CommonJS

// foo.js
var vs = require("value-schema");

ES Modules / Babel / TypeScript

// foo.mjs (ES Modules) / foo.js (Babel) / foo.ts (TypeScript)
import vs from "value-schema";

ES Modules has been supported as of Node.js v8.5.0. In Windows, Node.js v8.6.0 is recommended due to ERR_INVALID_PROTOCOL.

To execute "foo.mjs", --experimental-modules flag is required. (the flag is dropped as of Node.js v13.2.0)

$ node --experimental-modules foo.mjs
(node:25508) ExperimentalWarning: The ESM module loader is experimental.

TypeScript auto-completion and type-checking works perfectly on Visual Studio Code and IntelliJ IDEA!

Deno

Deno has been supported as of v3.

import vs from "https://deno.land/x/value_schema/mod.ts";       // latest version
import vs from "https://deno.land/x/value_schema@3/mod.ts";     // latest version of v3
import vs from "https://deno.land/x/value_schema@3.0.0/mod.ts"; // v3.0.0

CAUTION: specify value_schema (underscore) NOT value-schema (hyphen) because deno.land module database does not support name with hyphen!

Bun

Bun has been supported as of v3.

Use just like a npm module.

import vs from "value-schema";

Reference

types and constants

`ValueSchemaError`

The ValueSchemaError object represents an error.

ambient declaration

export interface ValueSchemaError extends Error
{
    name: string
    message: string
    cause: string
    value: any
    keyStack: (string | number)[]

    /**
     * check whether error is instance of ValueSchemaError or not
     * @param err error to check
     * @returns Yes/No
     */
    static is(err: unknown): err is ValueSchemaError;
}

properties

name	description
`name`	`"ValueSchemaError"`
`message`	human-readable description of the error, including a string `cause`
`cause`	cause of error; see `CAUSE`
`value`	value to apply
`keyStack`	array consists of path to key name(for object) or index(for array) that caused error; for nested object or array

See below example. For detail about schema / value-schema, see basic usage

import vs from "value-schema";
import assert from "assert";

// {foo: Array<{bar: {baz: number}}>}
const schemaObject = {
    foo: vs.array({
        each: vs.object({
            schemaObject: {
                bar: vs.object({
                    schemaObject: {
                        baz: vs.number(),
                    },
                }),
            },
        }),
    }),
};
const input = {
    foo: [
        {
            bar: {
                baz: 1,
            },
        },
        {
            bar: {
                baz: 2,
            },
        },
        { // index 2
            bar: {
                baz: "three", // ERROR!
            },
        },
        {
            bar: {
                baz: 4,
            },
        },
    ],
};
assert.throws(
    () => {
        vs.applySchemaObject(schemaObject, input);
    },
    {
        name: "ValueSchemaError",
        cause: vs.CAUSE.TYPE,
        keyStack: ["foo", 2, "bar", "baz"], // route to error key/index: object(key="foo") -> array(index=2) -> object(key="bar") -> object(key="baz")
    });

`CAUSE`

The cause of error.

For more information, see below examples.

`NUMBER.INTEGER`

Rounding mode.

For more information, see number.

`NUMERIC_STRING.CHECKSUM_ALGORITHM`

Checksum algorithms for numeric string.

For more information, see numeric string.

`STRING.PATTERN`

Regular expressions for string.

For more information, see string.

basic usage

`applySchemaObject(schemaObject, input[, onError[, onFinished]])`

apply schemaObject to data.

`data`

An object to be applied schema; e.g., req.query, req.body (in Express)

data will NOT be overwritten.

`schemaObject`

Schema object.

key: property name of data
value: schema instance; see below examples

`onError(err)`

Callback function for each errors. If no errors, this function will not be called.

If this parameter is omitted, applySchemaObject() throws ValueSchemaError on first error and remaining adjusting process will be cancelled.

err
- an instance of ValueSchemaError
- err.keyStack indicates path to key name that caused error: (string | number)[]
returns
- an adjuted value
throws
- an exception that will thrown from applySchemaObject()
- remaining processes will be cancelled

`onFinished()`

Called after finished all error handlings. Will NOT called if no errors.

examples

successful

For more information, see below references about number(), string(), and so on.

const schemaObject = { // schema for input
    id: vs.number({ // number, >=1
        minValue: 1,
    }),
    name: vs.string({ // string, max 16 characters (trims if over)
        maxLength: {
            length: 16,
            trims: true,
        },
    }),
    age: vs.number({ // number, integer (rounds down toward zero), >=0
        integer: vs.NUMBER.INTEGER.FLOOR_RZ,
        minValue: 0,
    }),
    email: vs.email(), // email
    state: vs.string({ // string, accepts only "active" and "inactive"
        only: ["active", "inactive"],
    }),
    classes: vs.array({ // array of number, separated by ",", ignores errors
        separatedBy: ",",
        each: {
            schema: vs.number(),
            ignoresErrors: true,
        },
    }),
    skills: vs.array({ // array of string, separated by ",", ignores errors
        separatedBy: ",",
        each: {
            schema: vs.string(),
            ignoresErrors: true,
        },
    }),
    creditCard: vs.numericString({ // numeric string, separated by "-", checks by Luhn algorithm
        separatedBy: "-",
        checksum: vs.NUMERIC_STRING.CHECKSUM_ALGORITHM.CREDIT_CARD,
    }),
    remoteAddr: vs.string({ // IPv4
        pattern: vs.STRING.PATTERN.IPV4,
    }),
    remoteAddrIpv6: vs.string({ // IPv6
        pattern: vs.STRING.PATTERN.IPV6,
    }),
    limit: vs.number({ // number, integer, omittable (sets 10 if omitted), >=1 (sets 1 if less), <=100 (sets 100 if greater)
        ifUndefined: 10,
        integer: true,
        minValue: {
            value: 1,
            adjusts: true,
        },
        maxValue: {
            value: 100,
            adjusts: true,
        },
    }),
    offset: vs.number({ // number, integer, omittable (sets 0 if omitted), >=0 (sets 0 if less)
        ifUndefined: 0,
        integer: true,
        minValue: {
            value: 0,
            adjusts: true,
        },
    }),
};
const input = { // input values
    id: "1",
    name: "Pablo Diego José Francisco de Paula Juan Nepomuceno María de los Remedios Ciprin Cipriano de la Santísima Trinidad Ruiz y Picasso",
    age: 20.5,
    email: "picasso@example.com",
    state: "active",
    classes: "1,3,abc,4",
    skills: "c,c++,javascript,python,,swift,kotlin",
    creditCard: "4111-1111-1111-1111",
    remoteAddr: "127.0.0.1",
    remoteAddrIpv6: "::1",
    limit: "0",
};
const expected = { // should be converted to this
    id: 1,
    name: "Pablo Diego José",
    age: 20,
    email: "picasso@example.com",
    state: "active",
    classes: [1, 3, 4],
    skills: ["c", "c++", "javascript", "python", "swift", "kotlin"],
    creditCard: "4111111111111111",
    remoteAddr: "127.0.0.1",
    remoteAddrIpv6: "::1",
    limit: 1,
    offset: 0,
};

// Let's apply!
const actual = vs.applySchemaObject(schemaObject, input);

// verification
assert.deepStrictEqual(actual, expected);

In TypeScript, type inference and auto-completion work perfectly!

error handling 1

fix errors

import vs from "value-schema";
import assert from "assert";

const schemaObject = {
    id: vs.number({
        minValue: 1,
    }),
    name: vs.string({
        maxLength: {
            length: 16,
            trims: true,
        },
    }),
    email: vs.email(),
};
const input = {
    id: 0, // error! (>= 1)
    name: "", // error! (empty string is not allowed)
    email: "john@example.com", // OK
};
const expected = {
    id: 100,
    name: "John Doe",
    email: "john@example.com",
};

const actual = vs.applySchemaObject(schemaObject, input, (err) => {
    const key = err.keyStack.shift();
    switch(key) {
    case "id":
        return 100;
    case "name":
        return "John Doe";
    default:
        return null;
    }
});
assert.deepStrictEqual(actual, expected);

error handling 2

throw exception after finished

import vs from "value-schema";
import assert from "assert";

const schemaObject = {
    id: vs.number({
        minValue: 1,
    }),
    name: vs.string({
        maxLength: {
            length: 16,
            trims: true,
        },
    }),
    email: vs.email(),
};
const input = {
    id: 0, // error! (>= 1)
    name: "", // error! (empty string is not allowed)
    email: "john@example.com", // OK
};

assert.throws(() => {
    const messages = [];
    vs.applySchemaObject(schemaObject, input, (err) => {
        // append key name
        const key = err.keyStack.shift();
        if(key !== undefined) {
            messages.push(key);
        }
    }, () => {
        // finished; join key name as message
        throw Error(messages.sort().join(","));
    });
}, {
    name: "Error",
    message: "id,name",
});

error handling 3

catch a first error by omitting error handler

import vs from "value-schema";
import assert from "assert";

const schemaObject = {
    id: vs.number({
        minValue: 1,
    }),
    name: vs.string({
        maxLength: {
            length: 16,
            trims: true,
        },
    }),
    email: vs.email(),
};
const input = {
    id: 0, // error! (>= 1)
    name: "", // error! (empty string is not allowed)
    email: "john@example.com", // OK
};

assert.throws(() => {
    // throws first error
    vs.applySchemaObject(schemaObject, input);
}, {
    name: "ValueSchemaError",
    cause: vs.CAUSE.MIN_VALUE,
    value: 0,
    keyStack: ["id"],
});

error handling 4

when input value is not an object

NOTE: schemaObject won't be checked because it's predictable; generated by programmer, not an external input

import vs from "value-schema";
import assert from "assert";

const schemaObject = {};
const input = 123;

assert.throws(() => {
    // `input` must be an object
    vs.applySchemaObject(schemaObject, input);
}, {
    name: "ValueSchemaError",
    cause: vs.CAUSE.TYPE,
    value: 123,
    keyStack: [],
});

boolean

ambient declarations

export function boolean(options?: OptionsForBoolean): BooleanSchema;

type OptionsForBoolean = {
    strictType?: boolean;
    acceptsAllNumbers?: boolean;

    ifUndefined?: boolean | null;
    ifEmptyString?: boolean | null;
    ifNull?: boolean | null;
}
type ErrorHandler = (err: ValueSchemaError) => boolean | null | never;
interface BooleanSchema {
    applyTo(value: unknown, onError?: ErrorHandler): boolean | null
}

`applyTo(value[, onError])`

Applies schema to value.

If an error occurs, this method calls onError (if specified) or throw ValueSchemaError (otherwise).

// should be OK
assert.strictEqual(
    vs.boolean().applyTo(true),
    true);
assert.strictEqual(
    vs.boolean().applyTo(false),
    false);

// should be adjusted
assert.strictEqual(
    vs.boolean().applyTo(1),
    true);
assert.strictEqual(
    vs.boolean().applyTo(0),
    false);
assert.strictEqual(
    vs.boolean().applyTo("1"),
    true);
assert.strictEqual(
    vs.boolean().applyTo("0"), // "0" is truthy in JavaScript, but value-schema treats as false!
    false);

// other truthy values
for (const truthy of ["true", "TRUE", "yes", "YES", "on", "ON"]) {
    assert.strictEqual(
        vs.boolean().applyTo(truthy),
        true);
}
// other falsy values
for (const falsy of ["false", "FALSE", "no", "NO", "off", "OFF"]) {
    assert.strictEqual(
        vs.boolean().applyTo(falsy),
        false);
}

// should cause error
assert.throws(
    () => vs.boolean().applyTo(-1), // accepts only 0,1
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.boolean().applyTo("abc"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.boolean().applyTo([]),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.boolean().applyTo({}),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

options

`strictType`

Enable strict type check. defaults: false

HANDLE WITH CARE! In URL encoding, all values will be treated as string. Use this method when your system accepts ONLY JSON encoding (application/json)

// should cause error
assert.throws(
    () => vs.boolean({strictType: true}).applyTo(1),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.boolean({strictType: true}).applyTo("1"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.boolean({strictType: true}).applyTo("true"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`acceptsAllNumbers`

Accepts all numbers or not, other than 0 / 1. defaults: false

// should be adjusted
assert.strictEqual(
    vs.boolean({acceptsAllNumbers: true}).applyTo(-1),
    true);
assert.strictEqual(
    vs.boolean({acceptsAllNumbers: true}).applyTo("100"),
    true);

`ifUndefined`

Specifies return value when input value is undefined.

// should be adjusted
assert.strictEqual(
    vs.boolean({ifUndefined: true}).applyTo(undefined),
    true);

// should cause error
assert.throws(
    () => vs.boolean().applyTo(undefined),
    {name: "ValueSchemaError", cause: vs.CAUSE.UNDEFINED});

`ifNull`

Specifies return value when input value is null.

// should be adjusted
assert.strictEqual(
    vs.boolean({ifNull: true}).applyTo(null),
    true);

// should cause error
assert.throws(
    () => vs.boolean().applyTo(null),
    {name: "ValueSchemaError", cause: vs.CAUSE.NULL});

`ifEmptyString`

Specifies return value when input value is "".

// should be adjusted
assert.strictEqual(
    vs.boolean({ifEmptyString: true}).applyTo(""),
    true);

// should cause error
assert.throws(
    () => vs.boolean().applyTo(""),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

number

ambient declarations

export function number(options?: OptionsForNumber): NumberSchema;

type OptionsForNumber = {
    strictType?: boolean;
    acceptsSpecialFormats?: boolean;
    acceptsFullWidth?: boolean;

    ifUndefined?: number | null;
    ifEmptyString?: number | null;
    ifNull?: number | null;

    integer?: boolean | NUMBER.INTEGER;
    only?: number[];
    minValue?: number | {value: number, adjusts: boolean};
    maxValue?: number | {value: number, adjusts: boolean};

    converter?: (value: number, fail: () => never) => number;
}
type ErrorHandler = (err: ValueSchemaError) => number | null | never;
interface NumberSchema {
    applyTo(value: unknown, onError?: ErrorHandler): number | null
}

`applyTo(value[, onError])`

Applies schema to value.

If an error occurs, this method calls onError (if specified) or throw ValueSchemaError (otherwise).

// should be OK
assert.strictEqual(
    vs.number().applyTo(-123),
    -123);

// should be adjusted
assert.strictEqual(
    vs.number().applyTo("-123"),
    -123);
assert.strictEqual(
    vs.number().applyTo(true),
    1);
assert.strictEqual(
    vs.number().applyTo(false),
    0);

// should cause error
assert.strictEqual( // catch error by callback function (that returns a value from applyTo() method)
    vs.number().applyTo(
        "abc",
        (err) => 10),
    10);
assert.throws( // ... or try-catch syntax
    () => vs.number().applyTo("abc"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.number().applyTo("true"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

options

`strictType`

Enable strict type check. defaults: false

HANDLE WITH CARE! In URL encoding, all values will be treated as string. Use this method when your system accepts ONLY JSON encoding (application/json)

// should be adjusted
assert.strictEqual(
    vs.number().applyTo("123"),
    123);
assert.strictEqual(
    vs.number().applyTo(true),
    1);

// should cause error
assert.throws(
    () => vs.number({strictType: true}).applyTo("123"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.number({strictType: true}).applyTo(true),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`ifUndefined`

Specifies return value when input value is undefined.

// should be adjusted
assert.strictEqual(
    vs.number({ifUndefined: 1}).applyTo(undefined),
    1);

// should cause error
assert.throws(
    () => vs.number().applyTo(undefined),
    {name: "ValueSchemaError", cause: vs.CAUSE.UNDEFINED});

`ifNull`

Specifies return value when input value is null.

// should be adjusted
assert.strictEqual(
    vs.number({ifNull: 1}).applyTo(null),
    1);

// should cause error
assert.throws(
    () => vs.number().applyTo(null),
    {name: "ValueSchemaError", cause: vs.CAUSE.NULL});

`ifEmptyString`

Specifies return value when input value is "".

// should be adjusted
assert.strictEqual(
    vs.number({ifEmptyString: 1}).applyTo(""),
    1);

// should cause error
assert.throws(
    () => vs.number().applyTo(""),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

`acceptsSpecialFormats`

Accepts all special number formats; e.g., "1e+2", "0x100", "0o100", "0b100". defaults: false

// should be adjusted
assert.strictEqual(
    vs.number({acceptsSpecialFormats: true}).applyTo("1e+2"),
    100);
assert.strictEqual(
    vs.number({acceptsSpecialFormats: true}).applyTo("0x100"),
    256);
assert.strictEqual(
    vs.number({acceptsSpecialFormats: true}).applyTo("0o100"),
    64);
assert.strictEqual(
    vs.number({acceptsSpecialFormats: true}).applyTo("0b100"),
    4);

// should cause error
assert.throws(
    () => vs.number().applyTo("1e+2"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`acceptsFullWidth`

Accepts full-width string; e.g., "１２３４．５", "1２3４.５". defaults: false

// should be adjusted
assert.strictEqual(
    vs.number({acceptsFullWidth: true}).applyTo("１２３４．５"),
    1234.5);

// should cause error
assert.throws(
    () => vs.number().applyTo("１２３４．５"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`integer`

Limits an input value to integer.

value	description
`NUMBER.INTEGER.NO` (`0`) / `false`	does not limit to integer
`NUMBER.INTEGER.YES` (`1`) / `true`	limits to integer, but does not round
`NUMBER.INTEGER.FLOOR` (`2`)	rounds towards −∞
`NUMBER.INTEGER.FLOOR_RZ` (`3`)	rounds towards 0
`NUMBER.INTEGER.CEIL` (`4`)	rounds towards +∞
`NUMBER.INTEGER.CEIL_RI` (`5`)	rounds towards ∞
`NUMBER.INTEGER.HALF_UP` (`6`)	rounds half towards +∞
`NUMBER.INTEGER.HALF_UP_RZ` (`7`)	rounds half towards 0
`NUMBER.INTEGER.HALF_DOWN` (`8`)	rounds half towards −∞
`NUMBER.INTEGER.HALF_DOWN_RZ` (`9`)	rounds half towards 0

// should be adjusted
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.FLOOR}).applyTo(3.14),
    3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.FLOOR}).applyTo("3.14"),
    3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.FLOOR}).applyTo(-3.14),
    -4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.FLOOR_RZ}).applyTo(3.14),
    3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.FLOOR_RZ}).applyTo(-3.14),
    -3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.CEIL}).applyTo(3.14),
    4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.CEIL}).applyTo(-3.14),
    -3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.CEIL_RI}).applyTo(3.14),
    4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.CEIL_RI}).applyTo(-3.14),
    -4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_UP}).applyTo(3.49),
    3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_UP}).applyTo(3.5),
    4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_UP}).applyTo(-3.5),
    -3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_UP}).applyTo(-3.51),
    -4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_UP_RZ}).applyTo(3.49),
    3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_UP_RZ}).applyTo(3.5),
    4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_UP_RZ}).applyTo(-3.49),
    -3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_UP_RZ}).applyTo(-3.5),
    -4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_DOWN}).applyTo(3.5),
    3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_DOWN}).applyTo(3.51),
    4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_DOWN}).applyTo(-3.49),
    -3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_DOWN}).applyTo(-3.5),
    -4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_DOWN_RZ}).applyTo(3.5),
    3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_DOWN_RZ}).applyTo(3.51),
    4);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_DOWN_RZ}).applyTo(-3.5),
    -3);
assert.strictEqual(
    vs.number({integer: vs.NUMBER.INTEGER.HALF_DOWN_RZ}).applyTo(-3.51),
    -4);

// should cause error
assert.throws(
    () => vs.number({integer: true}).applyTo(3.14),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.number({integer: vs.NUMBER.INTEGER.YES}).applyTo(3.14), // equivalent to "true"
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`only`

Accepts only particular values.

// should be OK
assert.strictEqual(
    vs.number({only: [1, 3, 5]}).applyTo(1),
    1);

// should cause error
assert.throws(
    () => vs.number({only: [1, 3, 5]}).applyTo(2),
    {name: "ValueSchemaError", cause: vs.CAUSE.ONLY});

`minValue`

Limits minimum value.

// should be adjusted
assert.strictEqual(
    vs.number({minValue: {value: 1, adjusts: true}}).applyTo(0),
    1);

// should cause errors
assert.throws(
    () => vs.number({minValue: {value: 1, adjusts: false}}).applyTo(0),
    {name: "ValueSchemaError", cause: vs.CAUSE.MIN_VALUE});
assert.throws(
    () => vs.number({minValue: 1}).applyTo(0), // shorthand of {value: 1, adjusts: false}
    {name: "ValueSchemaError", cause: vs.CAUSE.MIN_VALUE});

`maxValue`

Limits maximum value.

// should be adjusted
assert.strictEqual(
    vs.number({maxValue: {value: 100, adjusts: true}}).applyTo(101),
    100);

// should cause errors
assert.throws(
    () => vs.number({maxValue: {value: 100, adjusts: false}}).applyTo(101),
    {name: "ValueSchemaError", cause: vs.CAUSE.MAX_VALUE});
assert.throws(
    () => vs.number({maxValue: 100}).applyTo(101), // shorthand of {value: 100, adjusts: false}
    {name: "ValueSchemaError", cause: vs.CAUSE.MAX_VALUE});

`converter`

Converts input value to another.

fail() causes ValueSchemaError.

// should be adjusted
assert.strictEqual(
    vs.number({converter: value => value * 2}).applyTo("1"),
    2);

// should cause errors
assert.throws(
    () => vs.number({converter: (value, fail) => fail()}).applyTo(0),
    {name: "ValueSchemaError", cause: vs.CAUSE.CONVERTER});

string

ambient declarations

export function string(options?: OptionsForString): StringSchema;

type OptionsForString = {
    strictType?: boolean;

    ifUndefined?: string | null;
    ifEmptyString?: string | null;
    ifNull?: string | null;

    trims?: boolean;

    only?: string[];
    minLength?: number;
    maxLength?: number | {length: number, trims: boolean};
    pattern?: RegExp;

    converter?: (value: string, fail: () => never) => string;
}
type ErrorHandler = (err: ValueSchemaError) => string | null | never;
interface StringSchema {
    applyTo(value: unknown, onError?: ErrorHandler): string | null
}

`applyTo(value[, onError])`

Applies schema to value.

If an error occurs, this method calls onError (if specified) or throw ValueSchemaError (otherwise).

// should be OK
assert.strictEqual(
    vs.string().applyTo("123"),
    "123");

// should be adjusted
assert.strictEqual(
    vs.string().applyTo(123),
    "123");

// should cause error
assert.throws(
    () => vs.string().applyTo({}),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

options

`strictType`

Enable strict type check. defaults: false

// should be adjusted
assert.strictEqual(
    vs.string().applyTo(123),
    "123");
assert.strictEqual(
    vs.string().applyTo(true),
    "true");

// should cause error
assert.throws(
    () => vs.string({strictType: true}).applyTo(123),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.string({strictType: true}).applyTo(true),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`ifUndefined`

Specifies return value when input value is undefined.

// should be adjusted
assert.strictEqual(
    vs.string({ifUndefined: "xyz"}).applyTo(undefined),
    "xyz");

// should cause error
assert.throws(
    () => vs.string().applyTo(undefined),
    {name: "ValueSchemaError", cause: vs.CAUSE.UNDEFINED});

`ifNull`

Specifies return value when input value is null.

// should be adjusted
assert.strictEqual(
    vs.string({ifNull: "x"}).applyTo(null),
    "x");

// should cause error
assert.throws(
    () => vs.string().applyTo(null),
    {name: "ValueSchemaError", cause: vs.CAUSE.NULL});

`ifEmptyString`

Specifies return value when input value is undefined.

// should be adjusted
assert.strictEqual(
    vs.string({ifEmptyString: "xyz"}).applyTo(""),
    "xyz");

// should cause error
assert.throws(
    () => vs.string().applyTo(""),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

`trims`

Removes whitespace from both ends of input. defaults: false

// should be adjusted
assert.strictEqual(
    vs.string({trims: true}).applyTo("\r\n hell, word \t "),
    "hell, word");

// should cause error
assert.throws(
    () => vs.string({trims: true}).applyTo(" \t\r\n "),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

`only`

Accepts only particular values.

// should be OK
assert.strictEqual(
    vs.string({only: ["eat", "sleep", "play"]}).applyTo("sleep"),
    "sleep");
assert.strictEqual(
    vs.string({only: [""]}).applyTo(""),
    "");

// should cause error
assert.throws(
    () => vs.string({only: ["eat", "sleep", "play"]}).applyTo("study"),
    {name: "ValueSchemaError", cause: vs.CAUSE.ONLY});

`minLength`

Limits minimum length of input string.

// should be OK
assert.strictEqual(
    vs.string({minLength: 5}).applyTo("abcde"),
    "abcde");

// should cause error
assert.throws(
    () => vs.string({minLength: 5}).applyTo("a"),
    {name: "ValueSchemaError", cause: vs.CAUSE.MIN_LENGTH});

`maxLength`

Limits maximum length of an input string.

// should be OK
assert.strictEqual(
    vs.string({maxLength: {length: 5, trims: false}}).applyTo("abcde"),
    "abcde");

// should be adjusted
assert.strictEqual(
    vs.string({maxLength: {length: 5, trims: true}}).applyTo("abcdefg"),
    "abcde");

// should cause error
assert.throws(
    () => vs.string({maxLength: {length: 5, trims: false}}).applyTo("abcdefg"),
    {name: "ValueSchemaError", cause: vs.CAUSE.MAX_LENGTH});
assert.throws(
    () => vs.string({maxLength: 5}).applyTo("abcdefg"), // shorthand of {length: 5, trims: false}
    {name: "ValueSchemaError", cause: vs.CAUSE.MAX_LENGTH});

`pattern`

Specifies acceptable pattern by regular expression.

You can also use STRING.PATTERN constants

constant	explanation
`STRING.PATTERN.EMAIL`	email address that follows RFC5321 / RFC5322
`STRING.PATTERN.HTTP`	HTTP/HTTPS URL
`STRING.PATTERN.IPV4`	IPv4 address
`STRING.PATTERN.IPV6`	IPv6 address
`STRING.PATTERN.URI`	URI that follows RFC3986
`STRING.PATTERN.UUID`	UUID

// should be OK
assert.deepStrictEqual(
    vs.string({pattern: /^Node.js$/}).applyTo("NodeXjs"),
    "NodeXjs");
assert.deepStrictEqual(
    vs.string({pattern: vs.STRING.PATTERN.URI}).applyTo("https://example.com/path/to/resource?name=value#hash"),
    "https://example.com/path/to/resource?name=value#hash");


// should cause error
assert.throws(
    () => vs.string({pattern: /^Node.js$/}).applyTo("NODE.JS"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});
assert.throws(
    () => vs.string({pattern: vs.STRING.PATTERN.URI}).applyTo("https://例.com/"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});

`converter`

Converts input value to another.

fail() causes ValueSchemaError.

// should be adjusted
assert.strictEqual(
    vs.string({converter: value => value.toLowerCase()}).applyTo("123ABCxyz"),
    "123abcxyz");

// should cause errors
assert.throws(
    () => vs.string({converter: (value, fail) => fail()}).applyTo("foo"),
    {name: "ValueSchemaError", cause: vs.CAUSE.CONVERTER});

numeric string

ambient declarations

export function numericString(options?: OptionsForNumericString): NumericStringSchema;

type OptionsForNumericString = {
    ifUndefined?: string | null;
    ifEmptyString?: string | null;
    ifNull?: string | null;

    fullWidthToHalf?: boolean;
    joinsArray?: boolean;

    minLength?: number;
    maxLength?: number | {length: number, trims: boolean};
    separatedBy?: string | RegExp;
    pattern?: RegExp;
    checksum?: NUMERIC_STRING.CHECKSUM_ALGORITHM;

    converter?: (value: string, fail: () => never) => string;
}
type ErrorHandler = (err: ValueSchemaError) => string | null | never;
interface NumericStringSchema {
    applyTo(value: unknown, onError?: ErrorHandler): string | null
}

`applyTo(value[, onError])`

Applies schema to value.

If an error occurs, this method calls onError (if specified) or throw ValueSchemaError (otherwise).

// should be OK
assert.strictEqual(
    vs.numericString().applyTo("123"),
    "123");

// should be adjusted
assert.strictEqual(
    vs.numericString().applyTo(123),
    "123");

// should cause error
assert.throws(
    () => vs.numericString().applyTo("abc"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});

options

`ifUndefined`

Specifies return value when input value is undefined.

// should be adjusted
assert.strictEqual(
    vs.numericString({ifUndefined: "123"}).applyTo(undefined),
    "123");

// should cause error
assert.throws(
    () => vs.numericString().applyTo(undefined),
    {name: "ValueSchemaError", cause: vs.CAUSE.UNDEFINED});

`ifNull`

Specifies return value when input value is null.

// should be adjusted
assert.strictEqual(
    vs.numericString({ifNull: "456"}).applyTo(null),
    "456");

// should cause error
assert.throws(
    () => vs.numericString().applyTo(null),
    {name: "ValueSchemaError", cause: vs.CAUSE.NULL});

`ifEmptyString`

Specifies return value when input value is "".

// should be adjusted
assert.strictEqual(
    vs.numericString({ifEmptyString: "456"}).applyTo(""),
    "456");

// should cause error
assert.throws(
    () => vs.numericString().applyTo(""),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

`separatedBy`

Assumes an input value is separated by delimiter, and ignore them.

// should be adjusted
assert.strictEqual(
    vs.numericString({separatedBy: "-"}).applyTo("4111-1111-1111-1111"),
    "4111111111111111");

// should cause error
assert.throws(
    () => vs.numericString().applyTo("4111-1111-1111-1111"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});

`fullWidthToHalf`

Converts full-width string to half-width; e.g., "１２３４". defaults: false

// should be adjusted
assert.strictEqual(
    vs.numericString({fullWidthToHalf: true}).applyTo("１２３４"),
    "1234");

// should cause error
assert.throws(
    () => vs.numericString().applyTo("１２３４"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});

`joinsArray`

Assumes an input value is array, and join them. defaults: false

This method is useful for the following form.

<!-- "cc_number" will be passed in array -->
<form>
    Input credit card number:
    <input name="cc_number" required />
    -
    <input name="cc_number" required />
    -
    <input name="cc_number" required />
    -
    <input name="cc_number" required />
</form>

// should be adjusted
assert.strictEqual(
    vs.numericString({joinsArray: true}).applyTo(["1234", "5678"]),
    "12345678");

// should cause error
assert.throws(
    () => vs.numericString().applyTo(["1234", "5678"]),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`minLength`

Limits minimum length of input string.

// should be OK
assert.strictEqual(
    vs.numericString({minLength: 4}).applyTo("1234"),
    "1234");

// should cause error
assert.throws(
    () => vs.numericString({minLength: 5}).applyTo("1234"),
    {name: "ValueSchemaError", cause: vs.CAUSE.MIN_LENGTH});

`maxLength`

Limits maximum length of an input string.

// should be OK
assert.strictEqual(
    vs.numericString({maxLength: {length: 4, trims: false}}).applyTo("1234"),
    "1234");

// should be adjusted
assert.strictEqual(
    vs.numericString({maxLength: {length: 5, trims: true}, separatedBy: "-"}).applyTo("1234-5678"),
    "12345");

// should cause error
assert.throws(
    () => vs.numericString({maxLength: {length: 5, trims: false}}).applyTo("123456"),
    {name: "ValueSchemaError", cause: vs.CAUSE.MAX_LENGTH});
assert.throws(
    () => vs.numericString({maxLength: 5}).applyTo("123456"), // shorthand of {length: 5, trims: false}
    {name: "ValueSchemaError", cause: vs.CAUSE.MAX_LENGTH});

`checksum`

Checks input value by specified algorithm.

algorithm name	explanation	used by	constant	aliases
`"luhn"`	Luhn algorithm	credit card	`NUMERIC_STRING.CHECKSUM_ALGORITHM.LUHN`	`NUMERIC_STRING.CHECKSUM_ALGORITHM.CREDIT_CARD`
`"modulus10/weight3:1"`	Modulus 10 / Weight 3:1	ISBN-13, EAN, JAN	`NUMERIC_STRING.CHECKSUM_ALGORITHM.MODULUS10_WEIGHT3_1`	`NUMERIC_STRING.CHECKSUM_ALGORITHM.ISBN13` / `NUMERIC_STRING.CHECKSUM_ALGORITHM.EAN` / `NUMERIC_STRING.CHECKSUM_ALGORITHM.JAN`

// should be OK
assert.strictEqual(
    vs.numericString({checksum: vs.NUMERIC_STRING.CHECKSUM_ALGORITHM.LUHN}).applyTo("4111111111111111"),
    "4111111111111111");
assert.strictEqual(
    vs.numericString({checksum: vs.NUMERIC_STRING.CHECKSUM_ALGORITHM.CREDIT_CARD}).applyTo("4111111111111111"), // alias of LUHN
    "4111111111111111");
assert.strictEqual(
    vs.numericString({checksum: vs.NUMERIC_STRING.CHECKSUM_ALGORITHM.MODULUS10_WEIGHT3_1}).applyTo("9784101092058"),
    "9784101092058");
assert.strictEqual(
    vs.numericString({checksum: vs.NUMERIC_STRING.CHECKSUM_ALGORITHM.ISBN13}).applyTo("9784101092058"), // alias of MODULUS10_WEIGHT3_1
    "9784101092058");
assert.strictEqual(
    vs.numericString({checksum: vs.NUMERIC_STRING.CHECKSUM_ALGORITHM.EAN}).applyTo("9784101092058"), // alias of MODULUS10_WEIGHT3_1
    "9784101092058");
assert.strictEqual(
    vs.numericString({checksum: vs.NUMERIC_STRING.CHECKSUM_ALGORITHM.JAN}).applyTo("9784101092058"), // alias of MODULUS10_WEIGHT3_1
    "9784101092058");

// should cause error
assert.throws(
    () => vs.numericString({checksum: vs.NUMERIC_STRING.CHECKSUM_ALGORITHM.LUHN}).applyTo("4111111111111112"),
    {name: "ValueSchemaError", cause: vs.CAUSE.CHECKSUM});

`converter`

Converts input value to another.

fail() causes ValueSchemaError.

// should be adjusted
assert.strictEqual(
    vs.numericString({converter: value => value.padStart(8, "0")}).applyTo("1234"),
    "00001234");

// should cause errors
assert.throws(
    () => vs.numericString({converter: (value, fail) => fail()}).applyTo("1234"),
    {name: "ValueSchemaError", cause: vs.CAUSE.CONVERTER});

email

ambient declarations

export function email(options?: OptionsForEmail): EmailSchema;

type OptionsForEmail = {
    ifUndefined?: string | null;
    ifEmptyString?: string | null;
    ifNull?: string | null;

    trims?: boolean;
    pattern?: RegExp;
}
type ErrorHandler = (err: ValueSchemaError) => string | null | never;
interface EmailSchema {
    applyTo(value: unknown, onError?: ErrorHandler): string | null
}

`applyTo(value[, onError])`

Applies schema to value.

If an error occurs, this method calls onError (if specified) or throw ValueSchemaError (otherwise).

// should be OK
assert.strictEqual(
    vs.email().applyTo("user+mailbox/department=shipping@example.com"),
    "user+mailbox/department=shipping@example.com"); // dot-string
assert.strictEqual(
    vs.email().applyTo("!#$%&'*+-/=?^_`.{|}~@example.com"),
    "!#$%&'*+-/=?^_`.{|}~@example.com"); // dot-string
assert.strictEqual(
    vs.email().applyTo("\"Fred\\\"Bloggs\"@example.com"),
    "\"Fred\\\"Bloggs\"@example.com"); // quoted-string
assert.strictEqual(
    vs.email().applyTo("\"Joe.\\\\Blow\"@example.com"),
    "\"Joe.\\\\Blow\"@example.com"); // quoted-string
assert.strictEqual(
    vs.email().applyTo("user@example-domain.com"),
    "user@example-domain.com");
assert.strictEqual(
    vs.email().applyTo("user@example2.com"),
    "user@example2.com");

// should cause error
assert.throws(
    () => vs.email().applyTo("@example.com"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});
assert.throws(
    () => vs.email().applyTo(".a@example.com"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});
assert.throws(
    () => vs.email().applyTo("a.@example.com"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});
assert.throws(
    () => vs.email().applyTo("a..a@example.com"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});
assert.throws(
    () => vs.email().applyTo("user@example@com"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});
assert.throws(
    () => vs.email().applyTo("user-example-com"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});
assert.throws(
    () => vs.email().applyTo("user@example_domain.com"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});
assert.throws(
    () => vs.email().applyTo("user@example.com2"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});

options

`ifUndefined`

Specifies return value when input value is undefined.

// should be adjusted
assert.strictEqual(
    vs.email({ifUndefined: "user@example.com"}).applyTo(undefined),
    "user@example.com");

// should cause error
assert.throws(
    () => vs.email().applyTo(undefined),
    {name: "ValueSchemaError", cause: vs.CAUSE.UNDEFINED});

`ifNull`

Specifies return value when input value is null.

// should be adjusted
assert.strictEqual(
    vs.email({ifNull: "user@example.com"}).applyTo(null),
    "user@example.com");

// should cause error
assert.throws(
    () => vs.email().applyTo(null),
    {name: "ValueSchemaError", cause: vs.CAUSE.NULL});

`ifEmptyString`

Specifies return value when input value is "".

// should be adjusted
assert.strictEqual(
    vs.email({ifEmptyString: "user@example.com"}).applyTo(""),
    "user@example.com");

// should cause error
assert.throws(
    () => vs.email().applyTo(""),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

`trims`

Removes whitespace from both ends of input. defaults: false

// should be adjusted
assert.strictEqual(
    vs.email({trims: true}).applyTo("\r\n user@example.com \t "),
    "user@example.com");

// should cause error
assert.throws(
    () => vs.email().applyTo("\r\n user@example.com1 \t "),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});
assert.throws(
    () => vs.email({trims: true}).applyTo(" \t\r\n "),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

`pattern`

Specifies acceptable pattern by regular expression.

// should be OK
assert.strictEqual(
    vs.email({pattern: /^[\w\.]+@([\w\-]+\.)+\w+$/}).applyTo("......@example.com"), // accept leading/trailing/consecutively dots
    "......@example.com");

// should cause errors
assert.throws(
    () => vs.email().applyTo("......@example.com"),
    {name: "ValueSchemaError", cause: vs.CAUSE.PATTERN});

enumeration

Return type of applyTo() can be limited to enum-like type; enum and union. This is useful for TypeScript.

ambient declarations

export function enumeration<E = never>(options: OptionsForEnumeration): EnumerationSchema<E>;

type OptionsForEnumeration = {
    ifUndefined?: string | null;
    ifEmptyString?: string | null;
    ifNull?: string | null;

    only: E[]; // this is NOT an optional.
}
type ErrorHandler = (err: ValueSchemaError) => E | null | never;
interface EnumerationSchema {
    applyTo(value: unknown, onError?: ErrorHandler): E | null
}

`applyTo(value[, onError])`

Applies schema to value.

If an error occurs, this method calls onError (if specified) or throw ValueSchemaError (otherwise).

See example of only.

options

`only`

Accepts only particular values. This is NOT an optional.

// enum version
enum NumberEnum
{
    zero,
    one,
}
enum StringEnum
{
    a = "a",
    b = "b",
}

// should be OK
{
    // pattern 1: enum that contains number elements
    const val: NumberEnum = vs.enumeration({only: [NumberEnum.zero, NumberEnum.one]}).applyTo(1);
    assert.strictEqual(val, 1);
}
{
    // pattern 2: enum that contains only string elements
    const val: StringEnum = vs.enumeration({only: Object.values(StringEnum)}).applyTo("a");
    assert.strictEqual(val, "a");
}

// should cause error
assert.throws(
    () => vs.enumeration({only: Object.values(StringEnum)}).applyTo("c"),
    {name: "ValueSchemaError", cause: vs.CAUSE.ONLY});

// union version
type NumberUnion = 0 | 1;
type StringUnion = "a" | "b";

// should be OK
{
    // you can use "as const" for union type
    const val: NumberUnion = vs.enumeration({only: [0, 1] as const}).applyTo(1);
    assert.strictEqual(val, 1);
}
{
    // you can also use "<Type>"
    const val: StringEnum = vs.enumeration<StringUnion>({only: ["a", "b"]}).applyTo("a");
    assert.strictEqual(val, "a");
}

// should cause error
assert.throws(
    () => vs.enumeratino({only: ["a", "b"] as const}).applyTo("c"),
    {name: "ValueSchemaError", cause: vs.CAUSE.ONLY});

CAUTION: In union version, only must be "array of literal union types", "const-asserted array", or "array literal with generics".

type NumberUnion = 0 | 1;

// OK
{
    // array of literal union types
    const val: NumberUnion = vs.enumeration({only: [0, 1] as NumberUnion[]}).applyTo(1);
}
{
    // const-asserted array
    const val: NumberUnion = vs.enumeration({only: [0, 1] as const}).applyTo(1);
}
{
    // array literal with generics
    const val: NumberUnion = vs.enumeration<NumberUnion>({only: [0, 1]}).applyTo(1);
}

// NG (compile error)
{
    // TS2322: Type 'number' is not assignable to type 'NumberUnion'.
    const val: NumberUnion = vs.enumeration({only: [0, 1]}).applyTo(1); // number
}
{
    const only = [0, 1]; // number[]
    const val: NumberUnion = vs.enumeration({only: only}).applyTo(1);
}
{
    const only = [0, 1]; // number[]
    const val: NumberUnion = vs.enumeration<NumberUnion>({only: only}).applyTo(1);
}

`ifUndefined`

Specifies return value when input value is undefined.

enum StringEnum
{
    a = "a",
    b = "b",
}

// should be adjusted
assert.strictEqual(
    vs.enumeration({ifUndefined: StringEnum.a, only: Object.values(StringEnum)}).applyTo(undefined),
    "a");

// should cause error
assert.throws(
    () => vs.enumeration({only: Object.values(StringEnum)}).applyTo(undefined),
    {name: "ValueSchemaError", cause: vs.CAUSE.UNDEFINED});

`ifNull`

Specifies return value when input value is null.

enum StringEnum
{
    a = "a",
    b = "b",
}

// should be adjusted
assert.strictEqual(
    vs.enumeration({ifNull: StringEnum.a, only: Object.values(StringEnum)}).applyTo(null),
    "a");

// should cause error
assert.throws(
    () => vs.enumeration({only: Object.values(StringEnum)}).applyTo(null),
    {name: "ValueSchemaError", cause: vs.CAUSE.NULL});

`ifEmptyString`

Specifies return value when input value is "".

enum StringEnum
{
    a = "a",
    b = "b",
}

// should be adjusted
assert.strictEqual(
    vs.enumeration({ifEmptyString: StringEnum.a, only: Object.values(StringEnum)}).applyTo(""),
    "a");

// should cause error
assert.throws(
    () => vs.enumeration({only: Object.values(StringEnum)}).applyTo(""),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

array

ambient declarations

export function array<T>(options?: OptionsForArray<T>): ArraySchema;

type OptionsForArray<T> = {
    ifUndefined?: T[] | null;
    ifEmptyString?: T[] | null;
    ifNull?: T[] | null;

    separatedBy?: string | RegExp;
    toArray?: boolean;
    minLength?: number;
    maxLength?: number | {length: number, trims: boolean};
    each?: BaseSchema<T> | {schema: BaseSchema<T>, ignoresErrors: boolean};

    converter?: (values: T[], fail: () => never) => T[];
}
type ErrorHandler<T> = (err: ValueSchemaError) => T[] | null | never;
interface ArraySchema<T> {
    applyTo(value: unknown, onError?: ErrorHandler): T[] | null
}

`applyTo(value[, onError])`

Applies schema to value.

If an error occurs, this method calls onError (if specified) or throw ValueSchemaError (otherwise).

// should be OK
assert.deepStrictEqual(
    vs.array().applyTo([1, "a"]),
    [1, "a"]);

// should cause error
assert.throws(
    () => vs.array().applyTo("abc"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.array().applyTo(0),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

options

`ifUndefined`

Specifies return value when input value is undefined.

// should be adjusted
assert.deepStrictEqual(
    vs.array({ifUndefined: [1, "a"]}).applyTo(undefined),
    [1, "a"]);

// should cause error
assert.throws(
    () => vs.array().applyTo(undefined),
    {name: "ValueSchemaError", cause: vs.CAUSE.UNDEFINED});

`ifNull`

Specifies return value when input value is null.

// should be adjusted
assert.deepStrictEqual(
    vs.array({ifNull: [1, "a"]}).applyTo(null),
    [1, "a"]);

// should cause error
assert.throws(
    () => vs.array().applyTo(null),
    {name: "ValueSchemaError", cause: vs.CAUSE.NULL});

`ifEmptyString`

Specifies return value when input value is "".

// should be adjusted
assert.deepStrictEqual(
    vs.array({ifEmptyString: [1, "a"]}).applyTo(""),
    [1, "a"]);

// should cause error
assert.throws(
    () => vs.array().applyTo(""),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

`separatedBy`

Assumes an input value is string and separated by delimiter.

If an input type is array, this option will be ignored.

// should be OK
assert.deepStrictEqual(
    vs.array({separatedBy: ","}).applyTo([1, 2, 3]),
    [1, 2, 3]);

// should be adjusted
assert.deepStrictEqual(
    vs.array({separatedBy: ","}).applyTo("1,2,3"),
    ["1", "2", "3"]);

// should cause error
assert.throws(
    () => vs.array().applyTo("1,2,3"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`toArray`

Converts an input value to array if not. defaults: false

// should be OK
assert.deepStrictEqual(
    vs.array({toArray: true}).applyTo([0]),
    [0]);

// should be adjusted
assert.deepStrictEqual(
    vs.array({toArray: true}).applyTo(0),
    [0]);

// should cause error
assert.throws(
    () => vs.array().applyTo(0),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`minLength`

Limits minimum length of input array.

// should be OK
assert.deepStrictEqual(
    vs.array({minLength: 2}).applyTo([1, 2]),
    [1, 2]);

// should cause errors
assert.throws(
    () => vs.array({minLength: 2}).applyTo([1]),
    {name: "ValueSchemaError", cause: vs.CAUSE.MIN_LENGTH});

`maxLength`

Limits maximum length of an input array.

// should be OK
assert.deepStrictEqual(
    vs.array({maxLength: {length: 2, trims: false}}).applyTo([1, 2]),
    [1, 2]);

// should be adjusted
assert.deepStrictEqual(
    vs.array({maxLength: {length: 2, trims: true}}).applyTo([1, 2, 3]),
    [1, 2]);

// should cause error
assert.throws(
    () => vs.array({maxLength: {length: 2, trims: false}}).applyTo([1, 2, 3]),
    {name: "ValueSchemaError", cause: vs.CAUSE.MAX_LENGTH});
assert.throws(
    () => vs.array({maxLength: 2}).applyTo([1, 2, 3]), // shorthand of {length: 1, trims: false}
    {name: "ValueSchemaError", cause: vs.CAUSE.MAX_LENGTH});

`each`

Apply schema for each elements.

// should be adjusted
assert.deepStrictEqual(
    vs.array({each: {schema: vs.number(), ignoresErrors: true}}).applyTo([true, "abc", 2]),
    [1, 2]);

// should cause error
assert.throws(
    () => vs.array({each: {schema: vs.number(), ignoresErrors: false}}).applyTo([true, "abc", 2]),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.array({each: vs.number()}).applyTo([true, "abc", 2]), // shorthand of {schema: vs.number(), ignoresErrors: false}
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`converter`

Converts input value to another.

fail() causes ValueSchemaError.

// should be adjusted
assert.deepStrictEqual(
    vs.array({each: vs.number(), separatedBy: ",", converter: values => values.sort()}).applyTo("4,1,5,2"),
    [1, 2, 4, 5]);

// should cause errors
assert.throws(
    () => vs.array({converter: (value, fail) => fail()}).applyTo([]),
    {name: "ValueSchemaError", cause: vs.CAUSE.CONVERTER});

object

ambient declarations

export function object(options?: OptionsForObject): ObjectSchema;

type OptionsForObject = {
    ifUndefined?: object | null;
    ifEmptyString?: object | null;
    ifNull?: object | null;

    schemaObject?: Record<string, BaseSchema>;

    converter?: (values: object, fail: () => never) => object;
}
type ErrorHandler = (err: ValueSchemaError) => object | null | never;
interface ObjectSchema {
    applyTo(value: unknown, onError?: ErrorHandler): object | null
}

`applyTo(value[, onError])`

Applies schema to value.

If an error occurs, this method calls onError (if specified) or throw ValueSchemaError (otherwise).

// should be OK
assert.deepStrictEqual(
    vs.object().applyTo({a: 1, b: 2}),
    {a: 1, b: 2});

// should cause error
assert.throws(
    () => vs.object().applyTo("abc"),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});
assert.throws(
    () => vs.object().applyTo(0),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`ifUndefined`

Specifies return value when input value is undefined.

// should be adjusted
assert.deepStrictEqual(
    vs.object({ifUndefined: {a: 1, b: 2}}).applyTo(undefined),
    {a: 1, b: 2});

// should cause error
assert.throws(
    () => vs.object().applyTo(undefined),
    {name: "ValueSchemaError", cause: vs.CAUSE.UNDEFINED});

`ifNull`

Specifies return value when input value is null.

// should be adjusted
assert.deepStrictEqual(
    vs.object({ifNull: {a: 1, b: 2}}).applyTo(null),
    {a: 1, b: 2});

// should cause error
assert.throws(
    () => vs.object().applyTo(null),
    {name: "ValueSchemaError", cause: vs.CAUSE.NULL});

`ifEmptyString`

Specifies return value when input value is "".

// should be adjusted
assert.deepStrictEqual(
    vs.object({ifEmptyString: {a: 1, b: 2}}).applyTo(""),
    {a: 1, b: 2});

// should cause error
assert.throws(
    () => vs.object().applyTo(""),
    {name: "ValueSchemaError", cause: vs.CAUSE.EMPTY_STRING});

`schemaObject`

Applies schemaObject to input value.

// should be OK
const schemaObject = {a: vs.number(), b: vs.string()};
assert.deepStrictEqual(
    vs.object({schemaObject}).applyTo({a: 1, b: "2"}),
    {a: 1, b: "2"});

// should be adjusted
assert.deepStrictEqual(
    vs.object({schemaObject}).applyTo({a: 1, b: 2}),
    {a: 1, b: "2"});

// should cause error
assert.throws(
    () => vs.object({schemaObject}).applyTo({a: "x", b: "2"}),
    {name: "ValueSchemaError", cause: vs.CAUSE.TYPE});

`converter`

Converts input value to another.

fail() causes ValueSchemaError.

Below example uses case package.

// should be adjusted
function keysToCamel(values) {
    return Object.entries(values).reduce((prev, [key, value]) => {
        return {
            ...prev,
            [Case.camel(key)]: value,
        };
    }, {});
}
const input = {
    "first name": "John",
    "last-name": "Doe",
    "credit_card": "4111111111111111",
};
const output = {
    firstName: "John",
    lastName: "Doe",
    creditCard: "4111111111111111",
}
assert.deepStrictEqual(
    vs.object({converter: keysToCamel}).applyTo(input),
    output);

// should cause errors
assert.throws(
    () => vs.object({converter: (value, fail) => fail()}).applyTo({}),
    {name: "ValueSchemaError", cause: vs.CAUSE.CONVERTER});

Changelog

See CHANGELOG.md.

value-schema

Table of Contents

Introduction

example

Install

Loading

CommonJS

ES Modules / Babel / TypeScript

Deno

Bun

Reference

types and constants

ValueSchemaError

ambient declaration

properties

CAUSE

NUMBER.INTEGER

NUMERIC_STRING.CHECKSUM_ALGORITHM

STRING.PATTERN

basic usage

applySchemaObject(schemaObject, input[, onError[, onFinished]])

data

schemaObject

onError(err)

onFinished()

examples

successful

error handling 1

error handling 2

error handling 3

error handling 4

boolean

ambient declarations

applyTo(value[, onError])

options

strictType

acceptsAllNumbers

ifUndefined

ifNull

ifEmptyString

number

ambient declarations

applyTo(value[, onError])

options

strictType

ifUndefined

ifNull

ifEmptyString

acceptsSpecialFormats

acceptsFullWidth

integer

only

minValue

maxValue

converter

string

ambient declarations

applyTo(value[, onError])

options

strictType

ifUndefined

ifNull

ifEmptyString

trims

only

minLength

maxLength

pattern

converter

numeric string

ambient declarations

applyTo(value[, onError])

options

ifUndefined

ifNull

ifEmptyString

separatedBy

fullWidthToHalf

joinsArray

minLength

`ValueSchemaError`

`CAUSE`

`NUMBER.INTEGER`

`NUMERIC_STRING.CHECKSUM_ALGORITHM`

`STRING.PATTERN`

`applySchemaObject(schemaObject, input[, onError[, onFinished]])`

`data`

`schemaObject`

`onError(err)`

`onFinished()`

`applyTo(value[, onError])`

`strictType`

`acceptsAllNumbers`

`ifUndefined`

`ifNull`

`ifEmptyString`

`applyTo(value[, onError])`

`strictType`

`ifUndefined`

`ifNull`

`ifEmptyString`

`acceptsSpecialFormats`

`acceptsFullWidth`

`integer`

`only`

`minValue`

`maxValue`

`converter`

`applyTo(value[, onError])`

`strictType`

`ifUndefined`

`ifNull`

`ifEmptyString`

`trims`

`only`

`minLength`

`maxLength`

`pattern`

`converter`

`applyTo(value[, onError])`

`ifUndefined`

`ifNull`

`ifEmptyString`

`separatedBy`

`fullWidthToHalf`

`joinsArray`

`minLength`

`maxLength`

`checksum`

`converter`

`applyTo(value[, onError])`

`ifUndefined`

`ifNull`

`ifEmptyString`

`trims`

`pattern`

`applyTo(value[, onError])`

`only`

`ifUndefined`

`ifNull`

`ifEmptyString`

`applyTo(value[, onError])`

`ifUndefined`

`ifNull`

`ifEmptyString`

`separatedBy`

`toArray`

`minLength`

`maxLength`

`each`

`converter`

`applyTo(value[, onError])`

`ifUndefined`

`ifNull`

`ifEmptyString`

`schemaObject`

`converter`