Reuse functions by prototype and apply in js

In this example, I reuse the pop function of Array.prototype to pop the first element of input arguments

var calculate = function(){
    var fn = Array.prototype.pop.apply(arguments);
    console.log(fn);
    return fn.apply(null, arguments);
};

var sum = function(){
    var total = 0;
    for(var i=0, l=arguments.length; i<l; i=i+1){
        total = total +arguments[i];
    }
    return total;
};

var diff = function(x, y){
    return x-y;
};


var sumResult = calculate(1,2,3,4,5, sum),
    diffResult = calculate(1,2, diff);

alert(sumResult);
alert(diffResult);