Question: If I have two associative arrays, what would be the most efficient way of doing a diff against their values?

For example, given:

```
  array1 = {
    foreground: 'red',
    shape: 'circle',
    background: 'yellow'
  };

  array2 = {
    foreground: 'red',
    shape: 'square',
    angle: '90',
    background: 'yellow'
  };

```

How would I check one against the other, such that the items *missing* **or** *additional* are the resulting array. In this case, if I wanted to compare array1 within array2, it would return:

```
array3 = {shape: 'circle'}

```

Whilst if I compared array2 within array1, it would return:

```
array3 = {shape: 'square', angle: '90'}

```

Thanks in advance for your help!

Answer: 
If you're familiar with PHP syntax, take a look at <http://phpjs.org/functions/index> which includes almost all PHP's array related functions converted into JavaScript – including [`array_diff`](http://phpjs.org/functions/array_diff:309)
This might be much more sophisticate than what you need, but you can try my jsondiffpatch lib that will diff any pair of javascript objects:

<https://github.com/benjamine/jsondiffpatch>

if you want to test it you can see it live in <http://benjamine.github.com/jsondiffpatch/demo/index.html>