Compare two Arrays Javascript - Associative

This is an old question, but since it comes up first in a google search for comparing arrays, I thought I would throw in an alternative solution that works even when the array has two different objects with the same values.

function arrays_equal(a, b) {    return JSON.stringify(a) == JSON.stringify(b);}

Note: This is order dependent, so if order doesn't matter, you can always do a sort ahead of time.

I think the following should do what you want:

function nrKeys(a) {    var i = 0;    for (key in a) {        i++;    }    return i;}function compareAssociativeArrays(a, b) {   if (a == b) {       return true;   }      if (nrKeys(a) != nrKeys(b)) {       return false;   }   for (key in a) {          if (a[key] != b[key]) {         return false;     }   }   return true;}

I really don't know if there is a nicer way to do it than the brute force approach:

function differences(a, b){  var dif = {};  for(key in a){ //In a and not in b    if(!b[key]){      dif[key] = a[key];    }  }  for(key in a){ //in a and b but different values    if(a[key] && b[key] && a[key]!=b[key]){      //I don't know what you want in this case...    }  }  for(key in b){ //in b and not in a    if(!a[key]){      dif[key] = b[key];    }  }  return dif;}

Also, they are objects, not arrays, and some properties will not be enumerable through for..in (like Array.length, for example), so take it into account for your application.