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						- ### Estraverse [](http://travis-ci.org/estools/estraverse)
 - 
 - Estraverse ([estraverse](http://github.com/estools/estraverse)) is
 - [ECMAScript](http://www.ecma-international.org/publications/standards/Ecma-262.htm)
 - traversal functions from [esmangle project](http://github.com/estools/esmangle).
 - 
 - ### Documentation
 - 
 - You can find usage docs at [wiki page](https://github.com/estools/estraverse/wiki/Usage).
 - 
 - ### Example Usage
 - 
 - The following code will output all variables declared at the root of a file.
 - 
 - ```javascript
 - estraverse.traverse(ast, {
 -     enter: function (node, parent) {
 -         if (node.type == 'FunctionExpression' || node.type == 'FunctionDeclaration')
 -             return estraverse.VisitorOption.Skip;
 -     },
 -     leave: function (node, parent) {
 -         if (node.type == 'VariableDeclarator')
 -           console.log(node.id.name);
 -     }
 - });
 - ```
 - 
 - We can use `this.skip`, `this.remove` and `this.break` functions instead of using Skip, Remove and Break.
 - 
 - ```javascript
 - estraverse.traverse(ast, {
 -     enter: function (node) {
 -         this.break();
 -     }
 - });
 - ```
 - 
 - And estraverse provides `estraverse.replace` function. When returning node from `enter`/`leave`, current node is replaced with it.
 - 
 - ```javascript
 - result = estraverse.replace(tree, {
 -     enter: function (node) {
 -         // Replace it with replaced.
 -         if (node.type === 'Literal')
 -             return replaced;
 -     }
 - });
 - ```
 - 
 - By passing `visitor.keys` mapping, we can extend estraverse traversing functionality.
 - 
 - ```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
 - };
 - estraverse.traverse(tree, {
 -     enter: function (node) { },
 - 
 -     // Extending the existing traversing rules.
 -     keys: {
 -         // TargetNodeName: [ 'keys', 'containing', 'the', 'other', '**node**' ]
 -         TestExpression: ['argument']
 -     }
 - });
 - ```
 - 
 - By passing `visitor.fallback` option, we can control the behavior when encountering unknown nodes.
 - 
 - ```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
 - };
 - estraverse.traverse(tree, {
 -     enter: function (node) { },
 - 
 -     // Iterating the child **nodes** of unknown nodes.
 -     fallback: 'iteration'
 - });
 - ```
 - 
 - When `visitor.fallback` is a function, we can determine which keys to visit on each node.
 - 
 - ```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
 - };
 - estraverse.traverse(tree, {
 -     enter: function (node) { },
 - 
 -     // Skip the `argument` property of each node
 -     fallback: function(node) {
 -         return Object.keys(node).filter(function(key) {
 -             return key !== 'argument';
 -         });
 -     }
 - });
 - ```
 - 
 - ### License
 - 
 - Copyright (C) 2012-2016 [Yusuke Suzuki](http://github.com/Constellation)
 -  (twitter: [@Constellation](http://twitter.com/Constellation)) and other contributors.
 - 
 - Redistribution and use in source and binary forms, with or without
 - modification, are permitted provided that the following conditions are met:
 - 
 -   * Redistributions of source code must retain the above copyright
 -     notice, this list of conditions and the following disclaimer.
 - 
 -   * Redistributions in binary form must reproduce the above copyright
 -     notice, this list of conditions and the following disclaimer in the
 -     documentation and/or other materials provided with the distribution.
 - 
 - THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 - AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 - IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 - ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
 - DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 - (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 - LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 - ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 - (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 - THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 
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