1  ### esutils [![Build Status](https://secure.travis-ci.org/estools/esutils.svg)](http://travis-ci.org/estools/esutils)
  2  esutils ([esutils](http://github.com/estools/esutils)) is
  3  utility box for ECMAScript language tools.
  4  
  5  ### API
  6  
  7  ### ast
  8  
  9  #### ast.isExpression(node)
 10  
 11  Returns true if `node` is an Expression as defined in ECMA262 edition 5.1 section
 12  [11](https://es5.github.io/#x11).
 13  
 14  #### ast.isStatement(node)
 15  
 16  Returns true if `node` is a Statement as defined in ECMA262 edition 5.1 section
 17  [12](https://es5.github.io/#x12).
 18  
 19  #### ast.isIterationStatement(node)
 20  
 21  Returns true if `node` is an IterationStatement as defined in ECMA262 edition
 22  5.1 section [12.6](https://es5.github.io/#x12.6).
 23  
 24  #### ast.isSourceElement(node)
 25  
 26  Returns true if `node` is a SourceElement as defined in ECMA262 edition 5.1
 27  section [14](https://es5.github.io/#x14).
 28  
 29  #### ast.trailingStatement(node)
 30  
 31  Returns `Statement?` if `node` has trailing `Statement`.
 32  ```js
 33  if (cond)
 34      consequent;
 35  ```
 36  When taking this `IfStatement`, returns `consequent;` statement.
 37  
 38  #### ast.isProblematicIfStatement(node)
 39  
 40  Returns true if `node` is a problematic IfStatement. If `node` is a problematic `IfStatement`, `node` cannot be represented as an one on one JavaScript code.
 41  ```js
 42  {
 43      type: 'IfStatement',
 44      consequent: {
 45          type: 'WithStatement',
 46          body: {
 47              type: 'IfStatement',
 48              consequent: {type: 'EmptyStatement'}
 49          }
 50      },
 51      alternate: {type: 'EmptyStatement'}
 52  }
 53  ```
 54  The above node cannot be represented as a JavaScript code, since the top level `else` alternate belongs to an inner `IfStatement`.
 55  
 56  
 57  ### code
 58  
 59  #### code.isDecimalDigit(code)
 60  
 61  Return true if provided code is decimal digit.
 62  
 63  #### code.isHexDigit(code)
 64  
 65  Return true if provided code is hexadecimal digit.
 66  
 67  #### code.isOctalDigit(code)
 68  
 69  Return true if provided code is octal digit.
 70  
 71  #### code.isWhiteSpace(code)
 72  
 73  Return true if provided code is white space. White space characters are formally defined in ECMA262.
 74  
 75  #### code.isLineTerminator(code)
 76  
 77  Return true if provided code is line terminator. Line terminator characters are formally defined in ECMA262.
 78  
 79  #### code.isIdentifierStart(code)
 80  
 81  Return true if provided code can be the first character of ECMA262 Identifier. They are formally defined in ECMA262.
 82  
 83  #### code.isIdentifierPart(code)
 84  
 85  Return true if provided code can be the trailing character of ECMA262 Identifier. They are formally defined in ECMA262.
 86  
 87  ### keyword
 88  
 89  #### keyword.isKeywordES5(id, strict)
 90  
 91  Returns `true` if provided identifier string is a Keyword or Future Reserved Word
 92  in ECMA262 edition 5.1. They are formally defined in ECMA262 sections
 93  [7.6.1.1](http://es5.github.io/#x7.6.1.1) and [7.6.1.2](http://es5.github.io/#x7.6.1.2),
 94  respectively. If the `strict` flag is truthy, this function additionally checks whether
 95  `id` is a Keyword or Future Reserved Word under strict mode.
 96  
 97  #### keyword.isKeywordES6(id, strict)
 98  
 99  Returns `true` if provided identifier string is a Keyword or Future Reserved Word
100  in ECMA262 edition 6. They are formally defined in ECMA262 sections
101  [11.6.2.1](http://ecma-international.org/ecma-262/6.0/#sec-keywords) and
102  [11.6.2.2](http://ecma-international.org/ecma-262/6.0/#sec-future-reserved-words),
103  respectively. If the `strict` flag is truthy, this function additionally checks whether
104  `id` is a Keyword or Future Reserved Word under strict mode.
105  
106  #### keyword.isReservedWordES5(id, strict)
107  
108  Returns `true` if provided identifier string is a Reserved Word in ECMA262 edition 5.1.
109  They are formally defined in ECMA262 section [7.6.1](http://es5.github.io/#x7.6.1).
110  If the `strict` flag is truthy, this function additionally checks whether `id`
111  is a Reserved Word under strict mode.
112  
113  #### keyword.isReservedWordES6(id, strict)
114  
115  Returns `true` if provided identifier string is a Reserved Word in ECMA262 edition 6.
116  They are formally defined in ECMA262 section [11.6.2](http://ecma-international.org/ecma-262/6.0/#sec-reserved-words).
117  If the `strict` flag is truthy, this function additionally checks whether `id`
118  is a Reserved Word under strict mode.
119  
120  #### keyword.isRestrictedWord(id)
121  
122  Returns `true` if provided identifier string is one of `eval` or `arguments`.
123  They are restricted in strict mode code throughout ECMA262 edition 5.1 and
124  in ECMA262 edition 6 section [12.1.1](http://ecma-international.org/ecma-262/6.0/#sec-identifiers-static-semantics-early-errors).
125  
126  #### keyword.isIdentifierNameES5(id)
127  
128  Return true if provided identifier string is an IdentifierName as specified in
129  ECMA262 edition 5.1 section [7.6](https://es5.github.io/#x7.6).
130  
131  #### keyword.isIdentifierNameES6(id)
132  
133  Return true if provided identifier string is an IdentifierName as specified in
134  ECMA262 edition 6 section [11.6](http://ecma-international.org/ecma-262/6.0/#sec-names-and-keywords).
135  
136  #### keyword.isIdentifierES5(id, strict)
137  
138  Return true if provided identifier string is an Identifier as specified in
139  ECMA262 edition 5.1 section [7.6](https://es5.github.io/#x7.6). If the `strict`
140  flag is truthy, this function additionally checks whether `id` is an Identifier
141  under strict mode.
142  
143  #### keyword.isIdentifierES6(id, strict)
144  
145  Return true if provided identifier string is an Identifier as specified in
146  ECMA262 edition 6 section [12.1](http://ecma-international.org/ecma-262/6.0/#sec-identifiers).
147  If the `strict` flag is truthy, this function additionally checks whether `id`
148  is an Identifier under strict mode.
149  
150  ### License
151  
152  Copyright (C) 2013 [Yusuke Suzuki](http://github.com/Constellation)
153   (twitter: [@Constellation](http://twitter.com/Constellation)) and other contributors.
154  
155  Redistribution and use in source and binary forms, with or without
156  modification, are permitted provided that the following conditions are met:
157  
158    * Redistributions of source code must retain the above copyright
159      notice, this list of conditions and the following disclaimer.
160  
161    * Redistributions in binary form must reproduce the above copyright
162      notice, this list of conditions and the following disclaimer in the
163      documentation and/or other materials provided with the distribution.
164  
165  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
166  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
167  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
168  ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
169  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
170  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
171  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
172  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
173  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
174  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.