#Walk

Use walk to visit AST nodes and edit them in place. It is exported by @swc-next/core and the standalone @swc-next/walker package.

#Remove debugger statements

Hooks are named after node types. A function runs when the walker enters that node:

import { parseSync, printSync, walk } from "@swc-next/core";

const { program } = parseSync("debugger; const answer = 42;");
walk(program, {
  DebuggerStatement(node, context) {
    context.remove();
  },
});
console.log(printSync(program).code); // const answer = 42;

Use context methods for structural edits. Simple values, such as an identifier's name, can be edited directly. Hooks must be synchronous.

#Collect information

Pass state as the third argument to share a result across hooks:

import { parseSync, walk } from "@swc-next/core";

const { program } = parseSync('import value from "example";');
const dependencies = [];
walk(program, {
  ImportDeclaration(node, context) {
    context.state.push(node.source.value);
  },
}, dependencies);
console.log(dependencies); // ["example"]

#Next steps

Generate code from the edited AST.

See the Walk API for inputs and return values, enter/leave hooks, context methods, and reusable walkers.