面向对象的JavaScript-006-Function.prototype.apply()的3种作用

1.

 // Function.prototype.apply()的作用
     // 1.Using apply to chain constructors
     Function.prototype.construct = function (aArgs) {
       var oNew = Object.create(this.prototype);
       this.apply(oNew, aArgs);
       return oNew;
     };
     // 或者The Object.create() method used above is relatively new. For an alternative method using closures, please consider the following alternative:
     Function.prototype.construct = function(aArgs) {
       var fConstructor = this, fNewConstr = function() {
         fConstructor.apply(this, aArgs);
       };
       fNewConstr.prototype = fConstructor.prototype;
       return new fNewConstr();
     };

     function MyConstructor() {
       for (var nProp = 0; nProp < arguments.length; nProp++) {
         this['property' + nProp] = arguments[nProp];
       }
     }

     var myArray = [4, 'Hello world!', false];
     var myInstance = MyConstructor.construct(myArray);

     console.log(myInstance);
     console.log(myInstance.property1);                // logs 'Hello world!'
     console.log(myInstance instanceof MyConstructor); // logs 'true'
     console.log(myInstance.constructor); 

     // 2.Using apply and built-in functions
     // min/max number in an array
     var numbers = [5, 6, 2, 3, 7];

     // using Math.min/Math.max apply
     var max = Math.max.apply(null, numbers);
     // This about equal to Math.max(numbers[0], ...)
     // or Math.max(5, 6, ...)

     var min = Math.min.apply(null, numbers);
     console.log(max);
     console.log(min);
     // vs. simple loop based algorithm
     max = -Infinity, min = +Infinity;

     for (var i = 0; i < numbers.length; i++) {
       if (numbers[i] > max) {
         max = numbers[i];
       }
       if (numbers[i] < min) {
         min = numbers[i];
       }
     }
     console.log(max);
     console.log(min);

     function minOfArray(arr) {
       var min = Infinity;
       var QUANTUM = 32768;

       for (var i = 0, len = arr.length; i < len; i += QUANTUM) {
         var submin = Math.min.apply(null, arr.slice(i, Math.min(i+QUANTUM, len)));
         min = Math.min(submin, min);
       }

       return min;
     }

     var min = minOfArray([5, 6, 2, 3, 7]);
     console.log(min);

     // 3.Using apply in "monkey-patching"
     // Apply can be the best way to monkey-patch a built-in function of Firefox, or JS libraries. Given someobject.foo function, you can modify the function in a somewhat hacky way, like so:
     var originalfoo = someobject.foo;
     someobject.foo = function() {
       // Do stuff before calling function
       console.log(arguments);
       // Call the function as it would have been called normally:
       originalfoo.apply(this, arguments);
       // Run stuff after, here.
     }