estree-toolkit

Tools for working with ESTree AST

Installation

``bash
npm i estree-toolkit

or

yarn add estree-toolkit
`

Usage

`js
// Supports both CommonJS and ES Modules
// ES Module
import { traverse, builders as b } from 'estree-toolkit';
// CommonJS
const { traverse, builders: b } = require('estree-toolkit');
`

Basic operations

$3

`js
const { traverse } = require('estree-toolkit');

traverse(ast, {
Program(path) {
// Do something with the path
}
});
`

$3

`js
const { builders: b } = require('estree-toolkit');

b.identifier('x'); // => { type: 'Identifier', name: 'x' }
`

$3

`js
const { traverse, is } = require('estree-toolkit');
const { parseModule } = require('meriyah');

const ast = parseModule(x = 0);

traverse(ast, {
AssignmentExpression(path) {
if (is.identifier(path.node.left, { name: 'x' })) {
// left is an identifier with name x
}
}
});
`

$3

`js
const { traverse, builders: b } = require('estree-toolkit');
const { parseModule } = require('meriyah');

const ast = parseModule('a = b');

traverse(ast, {
Identifier(path) {
if (path.node.name === 'a') {
path.replaceWith(b.identifier('c'));
}
}
});

// Now the AST represents - c = b
`

$3

`js
const { traverse } = require('estree-toolkit');

traverse(ast, {
// Enable scope
$: { scope: true },
Program(path) {
// path.scope is now available in all paths
}
});
`
#### Checking if a binding is available
`js
const { traverse } = require('estree-toolkit');
const { parseModule } = require('meriyah');

const ast = parseModule(
import { a } from 'source';

const { b, c: [d, { e }] } = a;
);

traverse(ast, {
$: { scope: true },
Program(path) {
path.scope.hasBinding('a') // => true
path.scope.hasBinding('b') // => true
path.scope.hasBinding('c') // => false
path.scope.hasBinding('d') // => true
path.scope.hasBinding('e') // => true
}
});
`
#### Getting all references of a binding
`js
const { traverse } = require('estree-toolkit');
const { parseModule } = require('meriyah');

const ast = parseModule(
import { a } from 'source';

fn(a);
s = a;
let obj = { a };
);

traverse(ast, {
$: { scope: true },
Program(path) {
// Returns all the paths that reference the binding a
path.scope.getBinding('a').references // => [NodePath, NodePath, NodePath]
}
});
`
#### Checking if a global has been used
`js
const { traverse } = require('estree-toolkit');
const { parseModule } = require('meriyah');

const ast = parseModule(
const fx = require('fx-mod');
);

traverse(ast, {
$: { scope: true },
Program(path) {
path.scope.hasGlobalBinding('require') // => true
}
});
`
#### Renaming a binding
`js
const { traverse } = require('estree-toolkit');
const { parseModule } = require('meriyah');

const ast = parseModule(
const a = 0

a.reload()
while (a.ok) a.run()
);

traverse(ast, {
$: { scope: true },
Program(path) {
// a -> b
path.scope.renameBinding('a', 'b')
}
});

// Output code:
// const b = 0
//
// b.reload()
// while (b.ok) b.run()
`

$3

There are several static utilities that you can use.
- evaluate\
Evaluates the given path.
`js
const { utils: u, traverse } = require('estree-toolkit');
// We are using meriyah but you can use any parser (like acorn)
const { parseModule } = require('meriyah');

traverse(parseModule(1 + 2), {
BinaryExpression(path) {
u.evaluate(path) // => { value: 3 }
}
});

traverse(parseModule(1 === 2), {
BinaryExpression(path) {
u.evaluate(path) // => { value: false }
}
});

traverse(parseModule(iDoNotKnowWhatThisIs === 55), {
BinaryExpression(path) {
u.evaluate(path) // => undefined
}
});

traverse(parseModule(
({
text: 'This is an object',
data: [1, 'two']
})
), {
ObjectExpression(path) {
u.evaluate(path) // => { value: { text: 'This is an object', data: [1, 'two'] } }
}
});

traverse(parseModule(1 > 5 ? 'YES' : 'NO'), {
ConditionalExpression(path) {
u.evaluate(path) // => { value: 'NO' }
}
});
`
- evaluateTruthy\
Evaluates the path for truthiness and returns true, false or undefined depending on
evaluation result.

There's more functionalities, please read the documentation.

Documentation

You can find the documentation at https://estree-toolkit.netlify.app/

Why another traverser?

I know there is Babel. But there are
other tools which are faster than Babel. For example, meriyah is 3x faster than @babel/parser, astring is up to 50x faster than @babel/generator`. But these tool only work with ESTree AST. I wanted to use these
faster alternatives for one of my projects but could not find any traverser with
batteries-included. So I built one myself, with awesome scope analysis, it has all the things that you would need for traversing an ESTree AST. Also, a little bit faster than Babel.

Need help?

If you need help in any kind of ESTree AST modification, then don't hesitate to open a new discussion in Q&A Discussions. I will try my best to help you :)

License

Licensed under the MIT License.