| # 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(node, parent, prop, index) { | |
| // some code happens | |
| }, | |
| leave(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 | |