Question

我正在研究一种扩展方法，用于在JavaScript中创建对象和函数的子类型。我正在努力了解这两条线的不同之处：

f.prototype = p;
f.prototype = new p（）;

我能否解释一下幕后实际发生的事情？

我的理解是当我传入一个对象时，如果我使用'new p（）;'调用的构造函数可能不存在。它是否正确？是否有办法合并任何此代码？

    function extend(p) {
        if (p == null) throw TypeError(); 

        var f = function() {}, 
            t = typeof p;

        if( t === 'object' ) {
            f.prototype = p;

            f.prototype.constructor = f;
            return new f();

        } else if( t === 'function' ) {
            f.prototype = new p(); 

            f.prototype.constructor = f;
            return f; 
        } else {
            throw TypeError();
        }
    }       

    // ==========================
    var Person = {
        firstName: 'John',
        lastName: 'Doe'
    };
    console.log( 'Person: ', Person );

    var Employee = extend( Person );
    Employee.prototype = {
        employeeID: 0
    }

    console.log( 'Employee: ', Employee );

    var Manager = extend( Employee );
    Manager.prototype.fireEveryone = function() {
        alert( 'Everyone is fired!!!!' );
    }
    console.log( 'Manager: ', Manager );

由于

Answer 1

虽然我也急切地期待看到回答这个问题的答案，但我建议你看一下ECMAScript 5中引入的新继承/ OOP机制，我认为就JavaScript来说更有凝聚力。关注。

更多信息：

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/defineProperties https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/defineProperty https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/create

Javascript继承扩展方法提示

1 个答案: