Q:

Compare two arrays for detect remove and add element

There is two array, 
One -> ["A","B","C","D"]
Two -> ["A","E","H","D"]

I need check array details. I mentioned array one is existing data (before updating) and array two is update data ( after update the array one). I need figure out which data is come into that array (array two ) and which  data is remove from that array (array one). 

A:

Look into http://underscorejs.org/#arrays functions, you need to use _.intersection and _.difference methods. It's pretty easy to code that functions by yourself if you don't want new dependencies
_.intersection(One, Two) -> not changed data
_.difference(Two, One) -> new data
_.difference(One, Two) -> removed data

