# Yahoo! UI Library

### yui 3.0.0

Yahoo! UI Library > yui > Lang
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## `static` Class Lang

Provides the language utilites and extensions used by the library

### Methods

#### isArray

`static boolean isArray ( o )`
Determines whether or not the provided item is an array. Returns false for array-like collections such as the function arguments collection or HTMLElement collection will return false. You can use @see Array.test if you want to

Parameters:
  `o <object>` The object to test

Returns: `boolean`
  true if o is an array

#### isBoolean

`static boolean isBoolean ( o )`
Determines whether or not the provided item is a boolean

Parameters:
  `o <object>` The object to test

Returns: `boolean`
  true if o is a boolean

#### isDate

`static boolean isDate ( o )`
Determines whether or not the supplied item is a date instance

Parameters:
  `o <object>` The object to test

Returns: `boolean`
  true if o is a date

#### isFunction

`static boolean isFunction ( o )`
Determines whether or not the provided item is a function Note: Internet Explorer thinks certain functions are objects: var obj = document.createElement("object"); Y.Lang.isFunction(obj.getAttribute) // reports false in IE var input = document.createElement("input"); // append to body Y.Lang.isFunction(input.focus) // reports false in IE You will have to implement additional tests if these functions matter to you.

Parameters:
  `o <object>` The object to test

Returns: `boolean`
  true if o is a function

#### isNull

`static boolean isNull ( o )`
Determines whether or not the provided item is null

Parameters:
  `o <object>` The object to test

Returns: `boolean`
  true if o is null

#### isNumber

`static boolean isNumber ( o )`
Determines whether or not the provided item is a legal number

Parameters:
  `o <object>` The object to test

Returns: `boolean`
  true if o is a number

#### isObject

`static boolean isObject ( o , failfn )`
Determines whether or not the provided item is of type object or function

Parameters:
  `o <object>` The object to test
  `failfn <boolean>` fail if the input is a function

Returns: `boolean`
  true if o is an object

#### isString

`static boolean isString ( o )`
Determines whether or not the provided item is a string

Parameters:
  `o <object>` The object to test

Returns: `boolean`
  true if o is a string

#### isUndefined

`static boolean isUndefined ( o )`
Determines whether or not the provided item is undefined

Parameters:
  `o <object>` The object to test

Returns: `boolean`
  true if o is undefined

#### isValue

`static boolean isValue ( o )`
A convenience method for detecting a legitimate non-null value. Returns false for null/undefined/NaN, true for other values, including 0/false/''

Parameters:
  `o <object>` The item to test

Returns: `boolean`
  true if it is not null/undefined/NaN || false

#### trim

`static string trim ( s )`
Returns a string without any leading or trailing whitespace. If the input is not a string, the input will be returned untouched.

Parameters:
  `s <string>` the string to trim

Returns: `string`
  the trimmed string

#### type

`string type ( o )`
Returns a string representing the type of the item passed in.

Parameters:
  `o <object>` the item to test

Returns: `string`
  the detected type

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