esutils ([esutils](http://github.com/estools/esutils)) is
utility box for ECMAScript language tools.
### API
### ast
#### ast.isExpression(node)
Returns true if `node` is an Expression as defined in ECMA262 edition 5.1 section
[11](https://es5.github.io/#x11).
#### ast.isStatement(node)
Returns true if `node` is a Statement as defined in ECMA262 edition 5.1 section
[12](https://es5.github.io/#x12).
#### ast.isIterationStatement(node)
Returns true if `node` is an IterationStatement as defined in ECMA262 edition
5.1 section [12.6](https://es5.github.io/#x12.6).
#### ast.isSourceElement(node)
Returns true if `node` is a SourceElement as defined in ECMA262 edition 5.1
section [14](https://es5.github.io/#x14).
#### ast.trailingStatement(node)
Returns `Statement?` if `node` has trailing `Statement`.
```js
if (cond)
consequent;
```
When taking this `IfStatement`, returns `consequent;` statement.
#### ast.isProblematicIfStatement(node)
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.
```js
{
type: 'IfStatement',
consequent: {
type: 'WithStatement',
body: {
type: 'IfStatement',
consequent: {type: 'EmptyStatement'}
}
},
alternate: {type: 'EmptyStatement'}
}
```
The above node cannot be represented as a JavaScript code, since the top level `else` alternate belongs to an inner `IfStatement`.
### code
#### code.isDecimalDigit(code)
Return true if provided code is decimal digit.
#### code.isHexDigit(code)
Return true if provided code is hexadecimal digit.
#### code.isOctalDigit(code)
Return true if provided code is octal digit.
#### code.isWhiteSpace(code)
Return true if provided code is white space. White space characters are formally defined in ECMA262.
#### code.isLineTerminator(code)
Return true if provided code is line terminator. Line terminator characters are formally defined in ECMA262.
#### code.isIdentifierStart(code)
Return true if provided code can be the first character of ECMA262 Identifier. They are formally defined in ECMA262.
#### code.isIdentifierPart(code)
Return true if provided code can be the trailing character of ECMA262 Identifier. They are formally defined in ECMA262.
### keyword
#### keyword.isKeywordES5(id, strict)
Returns `true` if provided identifier string is a Keyword or Future Reserved Word
in ECMA262 edition 5.1. They are formally defined in ECMA262 sections
[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),
respectively. If the `strict` flag is truthy, this function additionally checks whether
`id` is a Keyword or Future Reserved Word under strict mode.
#### keyword.isKeywordES6(id, strict)
Returns `true` if provided identifier string is a Keyword or Future Reserved Word
in ECMA262 edition 6. They are formally defined in ECMA262 sections
[11.6.2.1](http://ecma-international.org/ecma-262/6.0/#sec-keywords) and
