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- # estree-walker
- Simple utility for walking an [ESTree](https://github.com/estree/estree)-compliant AST, such as one generated by [acorn](https://github.com/marijnh/acorn).
- ## Installation
- ```bash
- npm i estree-walker
- ```
- ## Usage
- ```js
- var walk = require( 'estree-walker' ).walk;
- var acorn = require( 'acorn' );
- ast = acorn.parse( sourceCode, options ); // https://github.com/acornjs/acorn
- walk( ast, {
- enter: function ( node, parent, prop, index ) {
- // some code happens
- },
- leave: function ( node, parent, prop, index ) {
- // some code happens
- }
- });
- ```
- Inside the `enter` function, calling `this.skip()` will prevent the node's children being walked, or the `leave` function (which is optional) being called.
- Call `this.replace(new_node)` in either `enter` or `leave` to replace the current node with a new one.
- Call `this.remove()` in either `enter` or `leave` to remove the current node.
- ## Why not use estraverse?
- The ESTree spec is evolving to accommodate ES6/7. I've had a couple of experiences where [estraverse](https://github.com/estools/estraverse) was unable to handle an AST generated by recent versions of acorn, because it hard-codes visitor keys.
- estree-walker, by contrast, simply enumerates a node's properties to find child nodes (and child lists of nodes), and is therefore resistant to spec changes. It's also much smaller. (The performance, if you're wondering, is basically identical.)
- None of which should be taken as criticism of estraverse, which has more features and has been battle-tested in many more situations, and for which I'm very grateful.
- ## License
- MIT
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