[refactor] that = this. For better minification
[refactor] parseInt ignores 'px' by itself
[refactor] no need for closing div in $ el creation
[refactor] commented redundant function. $ mostly returns integers
[refactor] simplified if
in `(obj.length && obj.length === 0)` `=== 0` is unnecessary since 0 is falsy
[refactor] `array[-1]` gives us undefined. if is unnecessary
[refactor] better readability
[refactor] removed unused variable
[refactor] don't create $ window object every time
[refactor] removed unused variable
[refactor] no need to use `new Array`
1. `new Array` is slower
2. not all items of array are used - inefficient memory usage
3. dictionary is a better data structure here, because we don't need to loop through indexInView
[refactor] no need in indexInView ;)
1. less memory
2. removed for loop
[refactor] store items to it's own variable
1. minification
2. faster: no object property look up on every loop iteration
[refactor] let jquery look up parents
[refactor] faster and shorter array pop-loop (poop)
[refactor] $ append optimizations
[refactor] array pop loop
[refactor] caching $el into a variable
1. minification
2. performance
[refactor] removed redundant length check
1. minification
2. there are no cases then id is greater then length
[refactor] unused variable