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49 lines
1.6 KiB
Markdown
49 lines
1.6 KiB
Markdown
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# estree-walker
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Simple utility for walking an [ESTree](https://github.com/estree/estree)-compliant AST, such as one generated by [acorn](https://github.com/marijnh/acorn).
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## Installation
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```bash
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npm i estree-walker
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```
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## Usage
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```js
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var walk = require( 'estree-walker' ).walk;
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var acorn = require( 'acorn' );
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ast = acorn.parse( sourceCode, options ); // https://github.com/acornjs/acorn
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walk( ast, {
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enter: function ( node, parent, prop, index ) {
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// some code happens
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},
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leave: function ( node, parent, prop, index ) {
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// some code happens
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}
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});
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```
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Inside the `enter` function, calling `this.skip()` will prevent the node's children being walked, or the `leave` function (which is optional) being called.
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Call `this.replace(new_node)` in either `enter` or `leave` to replace the current node with a new one.
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Call `this.remove()` in either `enter` or `leave` to remove the current node.
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## Why not use estraverse?
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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.
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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.)
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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.
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## License
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MIT
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