1### Estraverse [![Build Status](https://secure.travis-ci.org/estools/estraverse.svg)](http://travis-ci.org/estools/estraverse) 2 3Estraverse ([estraverse](http://github.com/estools/estraverse)) is 4[ECMAScript](http://www.ecma-international.org/publications/standards/Ecma-262.htm) 5traversal functions from [esmangle project](http://github.com/estools/esmangle). 6 7### Documentation 8 9You can find usage docs at [wiki page](https://github.com/estools/estraverse/wiki/Usage). 10 11### Example Usage 12 13The following code will output all variables declared at the root of a file. 14 15```javascript 16estraverse.traverse(ast, { 17 enter: function (node, parent) { 18 if (node.type == 'FunctionExpression' || node.type == 'FunctionDeclaration') 19 return estraverse.VisitorOption.Skip; 20 }, 21 leave: function (node, parent) { 22 if (node.type == 'VariableDeclarator') 23 console.log(node.id.name); 24 } 25}); 26``` 27 28We can use `this.skip`, `this.remove` and `this.break` functions instead of using Skip, Remove and Break. 29 30```javascript 31estraverse.traverse(ast, { 32 enter: function (node) { 33 this.break(); 34 } 35}); 36``` 37 38And estraverse provides `estraverse.replace` function. When returning node from `enter`/`leave`, current node is replaced with it. 39 40```javascript 41result = estraverse.replace(tree, { 42 enter: function (node) { 43 // Replace it with replaced. 44 if (node.type === 'Literal') 45 return replaced; 46 } 47}); 48``` 49 50By passing `visitor.keys` mapping, we can extend estraverse traversing functionality. 51 52```javascript 53// This tree contains a user-defined `TestExpression` node. 54var tree = { 55 type: 'TestExpression', 56 57 // This 'argument' is the property containing the other **node**. 58 argument: { 59 type: 'Literal', 60 value: 20 61 }, 62 63 // This 'extended' is the property not containing the other **node**. 64 extended: true 65}; 66estraverse.traverse(tree, { 67 enter: function (node) { }, 68 69 // Extending the existing traversing rules. 70 keys: { 71 // TargetNodeName: [ 'keys', 'containing', 'the', 'other', '**node**' ] 72 TestExpression: ['argument'] 73 } 74}); 75``` 76 77By passing `visitor.fallback` option, we can control the behavior when encountering unknown nodes. 78 79```javascript 80// This tree contains a user-defined `TestExpression` node. 81var tree = { 82 type: 'TestExpression', 83 84 // This 'argument' is the property containing the other **node**. 85 argument: { 86 type: 'Literal', 87 value: 20 88 }, 89 90 // This 'extended' is the property not containing the other **node**. 91 extended: true 92}; 93estraverse.traverse(tree, { 94 enter: function (node) { }, 95 96 // Iterating the child **nodes** of unknown nodes. 97 fallback: 'iteration' 98}); 99``` 100 101When `visitor.fallback` is a function, we can determine which keys to visit on each node. 102 103```javascript 104// This tree contains a user-defined `TestExpression` node. 105var tree = { 106 type: 'TestExpression', 107 108 // This 'argument' is the property containing the other **node**. 109 argument: { 110 type: 'Literal', 111 value: 20 112 }, 113 114 // This 'extended' is the property not containing the other **node**. 115 extended: true 116}; 117estraverse.traverse(tree, { 118 enter: function (node) { }, 119 120 // Skip the `argument` property of each node 121 fallback: function(node) { 122 return Object.keys(node).filter(function(key) { 123 return key !== 'argument'; 124 }); 125 } 126}); 127``` 128 129### License 130 131Copyright (C) 2012-2016 [Yusuke Suzuki](http://github.com/Constellation) 132 (twitter: [@Constellation](http://twitter.com/Constellation)) and other contributors. 133 134Redistribution and use in source and binary forms, with or without 135modification, are permitted provided that the following conditions are met: 136 137 * Redistributions of source code must retain the above copyright 138 notice, this list of conditions and the following disclaimer. 139 140 * Redistributions in binary form must reproduce the above copyright 141 notice, this list of conditions and the following disclaimer in the 142 documentation and/or other materials provided with the distribution. 143 144THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 145AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 146IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 147ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY 148DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 149(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 150LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 151ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 152(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 153THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 154