Using jQuery to compare two arrays

Question

Hi all,

I have two arrays of JavaScript Objects that I'd like to compare to see if they are the same. The objects may not (and most likely will not) be in the same order in each array. Each array shouldn't have any more than 10 objects. I thought jQuery might have an elegant solution to this problem, but I wasn't able to find much online.

I know that a brute nested $.each(array, function(){}) solution could work, but is there any built in function that I'm not aware of?

Thanks.

Answer 1

I don't think there's a good "jQuery " way to do this, but if you need efficiency, map one of the arrays by a certain key (one of the unique object fields), and then do comparison by looping through the other array and comparing against the map, or associative array, you just built.

If efficiency is not an issue, just compare every object in A to every object in B. As long as |A| and |B| are small, you should be okay.

Answer 2

It's not native jQuery and not the slickest code by any means, but....

http://www.mail-archive.com/[email protected]/msg16923.html

function arrayMatch( a, b ) {
      var o = {};
      for( var i = a.length; --i >= 0; )
         o[ a[i] ] = true;
      for( var i = b.length; --i >= 0; )
         if( o[ b[i] ] )
            return true;
      return false;
   }

Answer 3

jQuery.fn.compare = function(t) {
    if (this.length != t.length) { return false; }
    var a = this.sort(),
        b = t.sort();
    for (var i = 0; t[i]; i++) {
     if (a[i] !== b[i]) { 
      return false;
     }
    }
    return true;
};

Updated: I updated the example to work as the OP intended (sorting the arrays), example:

var a = [0,2]
var b = [2,0]

alert($(a).compare(b));

should alert true;

Update 2: I cached the sorted arrays just for the good.

Answer 4

Well, if you want to compare only the contents of arrays, there's a useful jQuery function $.inArray()

var arr = [11, "String #1", 14, "String #2"];
var arr_true = ["String #1", 14, "String #2", 11]; // contents are the same as arr
var arr_false = ["String #1", 14, "String #2", 16]; // contents differ

function test(arr_1, arr_2) {
    var equal = arr_1.length == arr_2.length; // if array sizes mismatches, then we assume, that they are not equal
    if (equal) {
        $.each(arr_1, function (foo, val) {
            if (!equal) return false;
            if ($.inArray(val, arr_2) == -1) {
                equal = false;
            } else {
                equal = true;
            }
        });
    }
    return equal;
}

alert('Array contents are the same? ' + test(arr, arr_true)); //- returns true
alert('Array contents are the same? ' + test(arr, arr_false)); //- returns false