Merging associative arrays javascript

Question

What's the best/standard way of merging two associative arrays in javascript? Does everyone just do it by rolling their own for loop?

Answer 1

1. In Javascript there is no notion of associative array, there are objects
2. The only way to merge two objects is to loop for their properties and copy pointers to their values that are not primitive types and values for primitive types to another instance

Answer 2

This is how Prototype does it:

Object.extend = function(destination, source) {
    for (var property in source)
     destination[property] = source[property];
    return destination;
};

called as, for example:

var arr1　= { robert: "bobby", john: "jack" };
var arr2 = { elizabeth: "liz", jennifer: "jen" };

var shortnames = Object.extend(arr1,arr2);

Answer 3

do you want to overwrite a property if the names are the same but the values are not?

And do you want to permanently change one of the original objects,

or do you want a new merged object returned?

function mergedObject(obj1, obj2, force){
    for(var p in obj1) this[p]= obj1[p];
    for(var p in obj2){
     if(obj2.hasOwnProperty(p)){
      if(force || this[p]=== undefined) this[p]= obj2[p];
      else{
       n= 2;
       while(this[p+n]!== undefined)++n;
       this[p+n]= obj2[p];
      }
     }
    }
}

Answer 4

In dojo, the 2-objects/arrays "merge" would be dojo.mixin(destination, source) -- you can also mix multiple sources into one destination, etc -- see the mixin function's reference for details.

Answer 5

with jquery you can call $.extend

obj1 = {a: 1, b: 2};
obj2 = {a: 4, c: 110};

obj3 = $.extend(obj1, obj2); 

obj1 == obj3 == {a: 4, b: 2, c: 110}

(assoc. arrays are objects in js)

look here: http://api.jquery.com/jQuery.extend/