babel-traverse

babel-traverse

babel-traverse maintains the overall tree state, and is responsible for replacing, removing, and adding nodes.

Install

$ npm install --save babel-traverse

Usage

We can use it alongside Babylon to traverse and update nodes:

import * as babylon from "babylon";
import traverse from "babel-traverse";

const code = `function square(n) {
  return n * n;
}`;

const ast = babylon.parse(code);

traverse(ast, {
  enter(path) {
    if (path.isIdentifier({ name: "n" })) {
      path.node.name = "x";
    }
  }
});

:book: Read the full docs here

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recast

Recast is a JavaScript AST manipulation library that allows you to parse, modify, and print your code while preserving the original formatting as much as possible. It differs from babel-traverse in that it focuses more on preserving the code's original format and less on providing a comprehensive transformation toolkit.

esprima

Esprima is a high performance, standard-compliant ECMAScript parser that also allows you to traverse and analyze JavaScript code. Unlike babel-traverse, Esprima does not focus on transformations but rather on parsing and providing a detailed AST.