Question: I've got two arrays of objects, the difference between them is only that arrayAfter will have an element added:

```
var arrayBefore = [
  {"name":"Alan","height":"171","weight":"66"},
  {"name":"Ben","height":"182","weight":"90"}
 ];

var arrayAfter= [
  {"name":"Alan","height":"171","weight":"66"},
  {"name":"Ben","height":"182","weight":"90"},
  {"name":"Chris","height":"163","weight":"71"}
 ];

```

"name" is always unique!

How can I find out which one is the element that has been added? I've tried ending up using nested for loops, but this seems overcomplicated. 

I've also found the this nice idea:

```
var diff = $(arrayAfter).not(arrayBefore ).get();

```

However, that does not seem to work on arrays of objects straight ahead.

**Is there some easy way to get the difference?**

Answer: 
If only the name indicates uniqueness, you can do:

```
//Get a list of all the names in the before array
var beforeNames = arrayBefore.map(function(person) { return person.name });

//Filter the after array to only contain names not contained in the before array
var uniqueObjects = arrayAfter.filter(function(person) {
    return beforeNames.indexOf(person.name) === -1;
});

console.log(uniqueObjects); //[{"name":"Chris","height":"163","weight":"71"}]

```

Demo: <http://jsfiddle.net/tehgc8L5/>
For a generic method you can combine [`Array.prototype.filter()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter) with [`Array.prototype.reduce()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce) which iterates over the object keys:

```
arrayAfter.filter(function(after) {
    return !arrayBefore.reduce(function(found, before) {
        if (!found) {
            found = true;
            for (key in before) {
                if (before.hasOwnProperty(key)) {
                    found = found && (before[key] === after[key]);
                }
            }
        }
        return found;
    }, false);
}); //[{name: "Chris", height: "163", weight: "71"}]

```