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.
    }