In Javascript there are several ways to detect array(variable is an array). But through this post , I will tell you ony four different ways to detect variable is an array .
Below there are 4 different ways are :->
1) Array.isArray(object) -> obj will be checked .
Example ->
// right syntax which return true ->

 Array.isArray([ ]);<br>
    Array.isArray([ 1 ]);<br>
    Array.isArray([ new Array ]);<br>
    Array.isArray([ ]);<br>
    Array.isArray([ Array.prototype]); // Array.prototype itself is also an array

// wrong syntax which return false ->

  Array.isArray( );<br>
    Array.isArray({ });<br>
    Array.isArray( [ null ] );<br>
    Array.isArray( undefined );<br>
    Array.isArray( 20 );Array.isArray([ ]);<br>
    Array.isArray( Array );<br>
    Array.isArray( true );<br>
    Array.isArray( false );<br><br>

suppose if Array.isArray() is not availbale, then you can make a function to create Array.isArray() method.
code to create function is ->

if ( !Array.isArray)<br>
{<br>
           Array.isArray = function( argument/object )<br>
               return Object.prototype.toString.call( argument ) == '[ object Array ] ' ;<br>
};<br>
}<br><br>

2) using constructor checking
Example ->

function isArray( obj ){<br>
  return( typeof obj !== 'undefined' && obj && obj.constructor === Array ) // (===) will check the value as well as data type alos<br>

Note -> Constructor checking is very fast and accurate .But it fail to identify when it is inherited from an Array

3) using instanceof operator
Example ->

fuction isArray(obj){
    return obj instanceof Array ;<br>
}<br><br>

4) using Prototype toString check
Example ->

       isArray = function(obj){<br>
           return Object.prototype.toString.call(obj) =="[ object Array ] " ;<br>
}