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Synchronously execute a callback on every node of a file's AST and stop walking whenever you see fit.

npm install node-source-walk


const Walker = require('node-source-walk');

const walker = new Walker();

// Assume src is the string contents of myfile.js
// or the AST of an outside parse of myfile.js
walker.walk(src, node => {
  if (node.type === whateverImLookingFor) {
    // No need to keep traversing since we found what we wanted

By default, Walker will use @babel/parser (supporting ES6, JSX, Flow, and all other available @babel/parser plugins) and the sourceType: module, but you can change any of the defaults as follows:

const walker = new Walker({
  sourceType: 'script',
  // If you don't like experimental plugins
  plugins: [
  • The supplied options are passed through to the parser, so you can configure it according to @babel/parser's documentation.

Swap out the parser

If you want to supply your own parser, you can do:

const walker = new Walker({
  parser: mySweetParser
  • The custom parser must have a .parse method that takes in a string and returns an object/AST.
  • All of the other options supplied to the Walker constructor will be passed along as parser options to your chosen parser.


walk(src, callback)

  • Recursively walks the given src from top to bottom
  • src: the contents of a file or its (already parsed) AST
  • callback: a function that is called for every visited node
    • The argument passed to callback will be the currently visited node.

moonwalk(node, callback)

  • Recursively walks up an AST starting from the given node. This is a traversal that's in the opposite direction of walk and traverse
  • node: a valid AST node
  • callback: a function that is called for every node (specifically via visiting the parent(s) of every node recursively)
    • The argument passed to callback will be the currently visited node.


  • Halts further walking of the AST until another manual call of walk or moonwalk
  • This is super-beneficial when dealing with large source files (or ASTs)

traverse(node, callback)

  • Allows you to traverse an AST node and execute a callback on it
  • Callback should expect the first argument to be an AST node, similar to walk's callback


  • Uses the options supplied to Walker to parse the given source code string and return its AST using the configured parser (or @babel/parser by default).



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npm i node-source-walk

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  • pahen
  • xhmikosr
  • mrjoelkemp