函数中的 getter 和 setter (javascript)

Question

在这样的对象中使用 get 时，get 有效：

var people = {
  name: "Alex",
  get sayHi() {
    return `Hi, ${this.name}!`
    }
};

var person = people;

document.write(person.sayHi);

但是使用一个函数我得到一个错误。如何在这样的函数中使用 Getters 和 Setters？

function People2() {
  this.name = "Mike";
  get sayHi() {
    return `Hi, ${this.name}!`;
  }
};

var user = new People2();

document.write(user.sayHi);

Answer 1

例如，使用这个：

function People2() {
  this.name = "Mike";
  this.__defineGetter__("sayHi", function() {
    return `Hi, ${this.name}!`;
  });
};

Answer 2

您只能在类 (ES2015) 和对象文字中使用实际的 get 和 set 关键字。

ECMAScript 5

在 ES5 中，您通常会使用 Object.defineProperty 来实现您想要实现的目标：

function People2() {
    this.name = "Mike";
}
Object.defineProperty(People2.prototype, "sayHi", {
    get: function() {
        return "Hi, " + this.name + "!";
    }
});

ECMAScript 2015

在 ES2015 中，您还可以使用类来实现所需的行为：

class People2 {
    constructor() {
        this.name = "Mike";
    }
    get sayHi() {
        return `Hi, ${this.name}!`;
    }
}

Answer 3

你可以试试这个

<script>
function People2(name) {
  this.name = name;  
};

People2.prototype = {
  get sayHi() {
    return `Hi, ${this.name}!`;}
};

var user = new People2('Alex');

document.write(user.sayHi);
</script>

或者这个...

<script>
function people(name) {
    this.name = name;
};

Object.defineProperty(people.prototype, 'sayHi', {
    get: function() { return `Hi, ${this.name}!`; }
});

var person = new people('Alex');

document.write(person.sayHi);
</script>

Answer 4

如果您想定义一个属性像 name 这样的函数以获得更多控制，我们可以在函数本身上使用 Object.defineProperty 如下：

function people(name) {

    //this.name = name; //this can be modified freely by caller code! we don't have any control

    var _name = name; //use a private var to store input `name`
    Object.defineProperty(this, 'name', {
        get: function() { return _name; },  //we can also use `return name;` if we don't use `name` input param for other purposes in our code
        writable: false, //if we need it to be read-only
        //... other configs
    });

};

var person = new people('Alex');
console.log(person.name); //writes Alex

函数中的 getter 和 setter (javascript)

Getters and Setters in a function (javascript)

javascript

function

getter-setter

ECMAScript 5

ECMAScript 2015