babel-traverse maintains the overall tree state, and is responsible for replacing, removing, and adding nodes.
$ npm install --save babel-traverse
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"; } } });