5.0.0 • Public • Published

    node-source-walk CI npm npm

    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.

    Public Members

    walk(src, cb)

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

    moonwalk(node, cb)

    • 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
    • cb: a function that is called for every node (specifically via visiting the parent(s) of every node recursively)
      • The argument passed to cb 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, cb)

    • 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).




    npm i node-source-walk

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    • pahen
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