如何使程序更高效的执行？

var add = function (a, b) { 
return a + b; 
};
var lazy_sum = make_lazy(add, 2, 3);
Test.expect(lazy_sum() === 5, ‘Evaluates the expression when required‘);//这个是codewars网站特有的测试代码，自己运行要另行写
var double = function (n) { 
return n * 2; 
}; 
var lazy_value = make_lazy(double, 5);
Test.expect(lazy_value() === 10, ‘Evaluates the expression when required‘);
var superAdd = function () {
return Array.prototype.slice.apply(arguments).reduce(function (a, c) {
return a + c; }, 0);
};
var lazy_superSum = make_lazy(superAdd, 1, 2, 3, 4, 5);
Test.expect(lazy_superSum() === 15, ‘Evaluates the expression when required‘);

var make_lazy = function () {
  // TODO: implement this function
  var arg = arguments; 
  return function(){
  return arg[0].apply(this,Array.prototype.slice.call(arg,1));
  }
};

var obj1 = {
    var x = 1;
    var a_ fuc = function(arg){
       alert(arg);
    }
};
var obj2 = {
    var x = 1;
    var b_fuc = function(arg){
        console.log(arg);
    }
};
var a = obj1;
var b = obj2;
a.a_fuc.apply(b,2);