sarsamurmu
estree-toolkit
Tools for working with ESTree AST
Installation
npm i estree-toolkit
# or
yarn add estree-toolkitUsage
// 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
const { traverse } = require('estree-toolkit');
traverse(ast, {
Program(path) {
// Do something with the path
}
});Building Nodes
const { builders: b } = require('estree-toolkit');
b.identifier('x'); // => { type: 'Identifier', name: 'x' }Checking node types
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
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
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
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
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
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
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.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 returnstrue,falseorundefineddepending 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.