> For the complete documentation index, see [llms.txt](https://bryan-guner.gitbook.io/my-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bryan-guner.gitbook.io/my-docs/redux/repos/examples/real-world/node_modules/esrecurse.md). # esrecurse #### Esrecurse [![Build Status](https://travis-ci.org/estools/esrecurse.svg?branch=master)](https://travis-ci.org/estools/esrecurse) Esrecurse ([esrecurse](https://github.com/estools/esrecurse)) is [ECMAScript](https://www.ecma-international.org/publications/standards/Ecma-262.htm) recursive traversing functionality. #### Example Usage The following code will output all variables declared at the root of a file. ```javascript esrecurse.visit(ast, { XXXStatement: function (node) { this.visit(node.left); // do something... this.visit(node.right); } }); ``` We can use `Visitor` instance. ```javascript var visitor = new esrecurse.Visitor({ XXXStatement: function (node) { this.visit(node.left); // do something... this.visit(node.right); } }); visitor.visit(ast); ``` We can inherit `Visitor` instance easily. ```javascript class Derived extends esrecurse.Visitor { constructor() { super(null); } XXXStatement(node) { } } ``` ```javascript function DerivedVisitor() { esrecurse.Visitor.call(/* this for constructor */ this /* visitor object automatically becomes this. */); } util.inherits(DerivedVisitor, esrecurse.Visitor); DerivedVisitor.prototype.XXXStatement = function (node) { this.visit(node.left); // do something... this.visit(node.right); }; ``` And you can invoke default visiting operation inside custom visit operation. ```javascript function DerivedVisitor() { esrecurse.Visitor.call(/* this for constructor */ this /* visitor object automatically becomes this. */); } util.inherits(DerivedVisitor, esrecurse.Visitor); DerivedVisitor.prototype.XXXStatement = function (node) { // do something... this.visitChildren(node); }; ``` The `childVisitorKeys` option does customize the behaviour of `this.visitChildren(node)`. We can use user-defined node types. ```javascript // This tree contains a user-defined `TestExpression` node. var tree = { type: 'TestExpression', // This 'argument' is the property containing the other **node**. argument: { type: 'Literal', value: 20 }, // This 'extended' is the property not containing the other **node**. extended: true }; esrecurse.visit( ast, { Literal: function (node) { // do something... } }, { // Extending the existing traversing rules. childVisitorKeys: { // TargetNodeName: [ 'keys', 'containing', 'the', 'other', '**node**' ] TestExpression: ['argument'] } } ); ``` We can use the `fallback` option as well. If the `fallback` option is `"iteration"`, `esrecurse` would visit all enumerable properties of unknown nodes. Please note circular references cause the stack overflow. AST might have circular references in additional properties for some purpose (e.g. `node.parent`). ```javascript esrecurse.visit( ast, { Literal: function (node) { // do something... } }, { fallback: 'iteration' } ); ``` If the `fallback` option is a function, `esrecurse` calls this function to determine the enumerable properties of unknown nodes. Please note circular references cause the stack overflow. AST might have circular references in additional properties for some purpose (e.g. `node.parent`). ```javascript esrecurse.visit( ast, { Literal: function (node) { // do something... } }, { fallback: function (node) { return Object.keys(node).filter(function(key) { return key !== 'argument' }); } } ); ``` #### License Copyright (C) 2014 [Yusuke Suzuki](https://github.com/Constellation) (twitter: [@Constellation](https://twitter.com/Constellation)) and other contributors. 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