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
### Traversing an AST
```js
const { traverse } = require('estree-toolkit');
traverse(ast, {
Program(path) {
// Do something with the path
}
});
```
### Building Nodes
```js
const { builders: b } = require('estree-toolkit');
b.identifier('x'); // => { type: 'Identifier', name: 'x' }
```
### Checking node types
```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`
}
}
});
```
### Replacing a node
```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`
```
### Collecting scope information
```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()
```
### Utilities
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](https://github.com/babel/babel). But there are
other tools which are faster than Babel. For example, [`meriyah`](https://github.com/meriyah/meriyah) is 3x faster than [`@babel/parser`](https://www.npmjs.com/package/@babel/parser), [`astring`](https://github.com/davidbonnet/astring) is up to 50x faster than [`@babel/generator`](https://www.npmjs.com/package/@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](https://github.com/sarsamurmu/estree-toolkit/discussions/categories/q-a). I will try my best to help you :)
## License
Licensed under the [MIT License](/LICENSE).