With the following line, .apply is invoking the .call method with the calling context of .call being the .slice method, and the arguments collection passed as individual arguments.
Function.prototype.call.apply(Array.prototype.slice, arguments);
This effectively gives us this:
Array.prototype.slice.call(arguments[0], arguments[1], arguments[2] /*, etc */);
This means that .slice() will be invoked with the first item in the arguments object as the calling context, and the rest of the arguments as the normal arguments.
So if the content of arguments is something like this:
myarray, 0, 5
You're effectively ending up with this:
myarray.slice(0, 5)
It's basically a way of not having to do this:
var arr = arguments[0];
var rest = Array.prototype.slice(arguments, 1);
var result = arr.slice.apply(arr, rest);
