type_of

A global method written in typescript to fix the javascript typeof operator. This code is written as a module for the deno runtime.

Table of Contents

General Info

While programming many years with JavaScript, I've ran into many bugs using the typeof operator to check data types. The bugs have carried over to using TypeScript as well. I decided to research all the bugs and build an alternative typeof as a global method named type_of(). This module is created to work on the deno runtime.

Features

Below are the current features of the type_of module.

  • Proper undefined check
  • Proper null check
  • Can type check all common JavaScript primitive types.
  • Can type check all methods including anonymous arrow functions.
  • Can type check objects
  • Can type check arrays
  • Using extended option can return class names.
  • Can type check new JavaScript types like bigint and symbol.
  • Can type check internal JavaScript functions like eval, JSON, NaN, etc.
  • Has special boolean called extended for returning an object from typeof with name and type.
  • JavaScript Errors can return proper type and name.

Tech

  • Deno - version 1.25.0
  • TypeScript - version 4.7.4
  • V8 - version 10.4.132.20
  • Visual Studio Code - 1.70+

Screenshots

Visual Studio Code

Setup

Things you will need to get this module running. You will need to install Deno runtime for Javascript / TypeScript.

Installing code from github

    # git clone git@github.com:Codevendor/type_of.git

Installing code from deno.land

    # Coming soon

Usage

I will describe the general usage here. I built the code to use the common typeof operator practice, but fix the bugs while extending it with new features.

Global Method: type_of

Global Method Name
type_of( src: unknown )
type_of( src: unknown, extended: boolean = false )
Param Name Type Description
src any The unknown src to check type of.
extended boolean Returns type_of_value object with extra information like name.
Return Type(s) Description
string Returns a string from the type check of the src.
type_of_value When param (extended = true), returns an object with properties name and type.

Custom Type: type_of_value

TypeScript Type Type Description
type_of_value object A custom TypeScript type for holding an object's name and type.
Property Name Type Description
name string The constructor name for the object or function.
type string The type of the JavaScript value.

Javascript Primitive Types:

  • null
  • undefined
  • boolean
  • number
  • string
  • symbol
  • bigint

Javascript Complex Type:

  • object

Extended types in type_of module

  • array
  • anonymous functions
  • function names
  • class names
  • internal javascript function names
  • error names

Examples

Examples will be shown below, but can also be found as assertion tests in the mod_test.ts file.

Type: unknown

  • While type_of() cant check for unknown types that spit out ReferenceErrors, you can always be safe by starting your check like so. 
    window.foo && type_of(foo);

Type Response List

  • Below is response list for using the type_of() method as string response.
Example Response
type_of( undefined ) "undefined"
type_of( void 0 ) "undefined"
type_of( null ) "null"
type_of( true ) "boolean"
type_of( 12345 ) "number"
type_of( "foo" ) "string"
type_of( Symbol() ) "symbol"
type_of( BigInt('9007199254740995') ) "bigint"
type_of( [] ) "array"
type_of( {} ) "object"
type_of( JSON ) "json"
type_of( Math ) "math"
type_of( /a-z/ ) "regexp"
type_of( function foo() { } ) "function"
type_of( () => { } ) "function"
type_of( class foo { } ) "function"
type_of( NaN ) "number"
type_of( Infinity ) "number"
type_of( window ) "window"
type_of( globalThis ) "window"
type_of( eval ) "function"
type_of( Date ) "function"
type_of( Error ) "function"
type_of( new Error() ) "error"
type_of( new RangeError() ) "error"

Type Response List Extended

  • Below is an extended response list of type_of(src, true) method returning a type_of_value object.
Example Response
type_of( Date, true ).name "Date"
type_of( Date, true ).type "function"
type_of( eval, true ).name "eval"
type_of( eval, true ).type "function"
type_of( function foo(){}, true ).name "foo"
type_of( function foo(){}, true ).type "function"
type_of( () => {}, true ).name "anonymous"
type_of( () => {}, true ).type "function"
type_of( class foo {}, true ).name "foo"
type_of( class foo {}, true ).type "function"
type_of( Error, true ).name "Error"
type_of( Error, true ).type "function"
type_of( new Error(), true ).name "Error"
type_of( new Error(), true ).type "error"
type_of( RangeError, true ).name "RangeError"
type_of( RangeError, true ).type "function"
type_of( new RangeError(), true ).name "RangeError"
type_of( new RangeError(), true ).type "error"
type_of( new RangeError(), true ).name "RangeError"
type_of( new RangeError(), true ).type "error"

Project Status

Project is: in progress

Room for Improvement

  • More testing needs to be done.

To do:

  • Create deno.land module.
  • Update tutorial and code usage examples.

Acknowledgements

Contact

Created by @Codevendor - feel free to contact me!

License

This project is open source and available under the ... MIT License.