JavaScript 继承详解（四）_js面向对象

    // 定义Person类
    function Person(name) {
      this.name = name;
    }
    // 定义Person的原型方法
    Person.method("getName", function() {
      return this.name;
    }); 
    
    // 定义Employee类
    function Employee(name, employeeID) {
      this.name = name;
      this.employeeID = employeeID;
    }
    // 指定Employee类从Person类继承
    Employee.inherits(Person);
    // 定义Employee的原型方法
    Employee.method("getEmployeeID", function() {
      return this.employeeID;
    });
    Employee.method("getName", function() {
      // 注意，可以在子类中调用父类的原型方法
      return "Employee name: " + this.uber("getName");
    });
    // 实例化子类
    var zhang = new Employee("ZhangSan", "1234");
    console.log(zhang.getName());  // "Employee name: ZhangSan"
    

    function Person(name) {
      this.name = name;
    }
    Person.method("getName", function(prefix) {
      return prefix + this.name;
    });

    function Employee(name, employeeID) {
      this.name = name;
      this.employeeID = employeeID;
    }
    Employee.inherits(Person);
    Employee.method("getName", function() {
      // 注意，uber的第一个参数是要调用父类的函数名称，后面的参数都是此函数的参数
      // 个人觉得这样方式不如这样调用来的直观：this.uber("Employee name: ")
      return this.uber("getName", "Employee name: ");
    });
    var zhang = new Employee("ZhangSan", "1234");
    console.log(zhang.getName());  // "Employee name: ZhangSan"
    

    Function.prototype.method = function(name, func) {
      // this指向当前函数，也即是typeof(this) === "function"
      this.prototype[name] = func;
      return this;
    };
    

    Function.method('inherits', function (parent) {
      // 关键是这一段：this.prototype = new parent()，这里实现了原型的引用
      var d = {}, p = (this.prototype = new parent());
      
      // 只为子类的原型增加uber方法，这里的Closure是为了在调用uber函数时知道当前类的父类的原型（也即是变量 - v）
      this.method('uber', function uber(name) {
        // 这里考虑到如果name是存在于Object.prototype中的函数名的情况
        // 比如 "toString" in {} === true
        if (!(name in d)) {
          // 通过d[name]计数，不理解具体的含义
          d[name] = 0;
        }    
        var f, r, t = d[name], v = parent.prototype;
        if (t) {
          while (t) {
            v = v.constructor.prototype;
            t -= 1;
          }
          f = v[name];
        } else {
          // 个人觉得这段代码有点繁琐，既然uber的含义就是父类的函数，那么f直接指向v[name]就可以了
          f = p[name];
          if (f == this[name]) {
            f = v[name];
          }
        }
        d[name] += 1;
        // 执行父类中的函数name，但是函数中this指向当前对象
        // 同时注意使用Array.prototype.slice.apply的方式对arguments进行截断（因为arguments不是标准的数组，没有slice方法）
        r = f.apply(this, Array.prototype.slice.apply(arguments, [1]));
        d[name] -= 1;
        return r;
      });
      return this;
    });
    

    var zhang = new Employee("ZhangSan", "1234");
    console.log(zhang.getName());  // "Employee name: ZhangSan"
    console.log(zhang.constructor === Employee);  // false
    console.log(zhang.constructor === Person);   // true
    

    Function.prototype.inherits = function(parent) {
      this.prototype = new parent();
      this.prototype.constructor = this;
      this.prototype.uber = function(name) {
        f = parent.prototype[name];
        return f.apply(this, Array.prototype.slice.call(arguments, 1));
      };
    };
    

    function Person(name) {
      this.name = name;
    }
    Person.prototype.getName = function(prefix) {
      return prefix + this.name;
    };
    function Employee(name, employeeID) {
      this.name = name;
      this.employeeID = employeeID;
    }
    Employee.inherits(Person);
    Employee.prototype.getName = function() {
      return this.uber("getName", "Employee name: ");
    };
    var zhang = new Employee("ZhangSan", "1234");
    console.log(zhang.getName());  // "Employee name: ZhangSan"
    console.log(zhang.constructor === Employee);  // true