在 ES6 中创建多个构造函数

Question

在 ES5 中，可以为一个类创建多个构造函数，同时使用原型为两者保留公共部分，如下所示

function Book() {
    //just creates an empty book.
}


function Book(title, length, author) {
    this.title = title;
    this.Length = length;
    this.author = author;
}

Book.prototype = {
    ISBN: "",
    Length: -1,
    genre: "",
    covering: "",
    author: "",
    currentPage: 0,
    title: "",

    flipTo: function FlipToAPage(pNum) {
        this.currentPage = pNum;
    },

    turnPageForward: function turnForward() {
        this.flipTo(this.currentPage++);
    },

    turnPageBackward: function turnBackward() {
        this.flipTo(this.currentPage--);
    }
};

var books = new Array(new Book(), new Book("First Edition", 350, "Random"));

我想使用 ES6 类和构造函数语法实现相同的结果

class Book{
    constructore (){}
}

Answer 1

ECMAScript 不支持函数/构造函数重载。如果你仍然想破解它，你可以使用参数对象来做到这一点。

constructor(title, length, author) {
        if(!arguments.length) {
            // empty book
        }
        else {
            this.title = title;
            this.Length = length;
            this.author = author;
        }
    }