超類的Java語言調用方法

Question

我嘗試在學生對象中的hello函數中調用方法doSomething，而沒有原型，只需將其附加在此即可。 學生擴展Person對象。

function Person(name){
    this._name = name;
    this.doSomething = function () {
        console.log('doSomething');
     }
}

function Student (name, grade) {
    this._name = name;
    this._grade = grade;

    this.hello = function  () {
        //How i can call doSomething() here
    }
}

Answer 1

你需要.call()父在構造使Student擁有一切Person做，然后做this.doSomething()

function Student (name, grade) {
    Person.call(this, name); // extends
    this._grade = grade;

    this.hello = function  () {
        this.doSomething();
    };
}

然后您可以從學生實例調用hello() ：

var student = new Student("t","A")
student.hello(); // logs 'doSomething'

小提琴的例子

Answer 2

您的代碼應該是（帶有正確的JS類擴展名）：

function Person(name){
    this._name = name;
}
Person.prototype.doSomething = function() {
    console.log('doSomething');
}

function Student (name, grade) {
    this._name = name;
    this._grade = grade;
}
Student.prototype = Object.create(Person.prototype); // extends
Student.prototype.hello = function  () {
    // Just call it like this:
    this.doSomething();
}