Traverse AST
A simple module to travese an AST. Its specifcally designed to travel one made from https://esm.sh/@swc/wasm-web@1.3.50. Each Node (Statement or Expression) on the tree is called on a passed in function for you to potentionally modify and mutate.
Usage
There is also a traverseAsync if the function being passed in will be returning a promise.
import initSwc, { parse, print } from 'https://esm.sh/@swc/wasm-web@1.3.50'
import { traverse, NodeType } from 'https://deno.land/x/traverse_ast@v0.0.0'
await initSwc()
const ast = await parse(await Deno.readTextFile('./input.js'))
/*
Converting all:
x('div', null, [])
to:
({
type: 'div',
attributes: null,
children: []
})
*/
traverse(ast.body, node => {
// Guard against all nodes that aren't a function call for a specific function called "x"
// Best to return undefined/null if no modification was made to the provided node.
if (node.type !== 'CallExpression' || node.callee.type !== 'Identifier' || node.callee.value !== 'x')
return
// Creating a new node to replace the existing.
return {
type: 'ParenthesisExpression',
span,
expression: {
type: 'ObjectExpression',
span,
properties: [
{
type: 'KeyValueProperty',
key: {
type: 'Identifier',
span,
value: 'type',
optional: false
},
value: node.arguments[ 0 ].expression
},
{
type: 'KeyValueProperty',
key: {
type: 'Identifier',
span,
value: 'attributes',
optional: false
},
value: node.arguments[ 1 ].expression
},
{
type: 'KeyValueProperty',
key: {
type: 'Identifier',
span,
value: 'children',
optional: false
},
value: node.arguments[ 2 ].expression
}
]
}
// Can use NodeType to make sure you're compliant with SWC's structure.
} satisfies NodeType<'ParenthesisExpression'>
})
await Deno.writeTextFile('./output.js', (await print(ast)).code)