cheat sheets.

Function

Summary
-------
Every function in JavaScript is actually a `Function` object.

Methods
-------
apply - calls a function with a given `this` value and `arguments` 
        provided as an array.
  * syntax - fun.apply(thisArg[, argsArray])

call - calls a function with a given `this` value and arguments 
       provided individually.
  * syntax - fun.call(thisArg[, arg1[, arg2[, ...]]])