Object.assign构造函数中的getter和setter [英] Object.assign getters and setters in constructor

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本文介绍了Object.assign构造函数中的getter和setter的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我尝试通过 Object.assign 定义构造函数中的getter和setter:

I try to define getter and setter in constructor via Object.assign:

function Class() {
  Object.assign(this, {
    get prop() { console.log('call get') },
    set prop(v) { console.log('call set') },
  });
}

var c = new Class(); // (1) => 'call get'
console.log(c.prop); // (2) => undefined
c.prop = 'change';
console.log(c.prop); // (3) => 'change' 

问题:

( 1)为什么要调用getter?

(1) Why getter is called?

(2)为什么不调用getter?

(2) Why getter isn't called?

(3)为什么忽略setter?

(3) Why setter is ignored?

推荐答案

所有三个问题的答案都是一样的:对象。 assign 从源对象读取属性的,它不会复制getter / setters。

The answer to all three of your questions is the same: Object.assign reads the value of the property from the source object, it doesn't copy getters/setters.

你可以看到,如果你看一下属性描述符:

You can see that if you look at the property descriptor:

var source = {
  get prop() { },
  set prop(v) { }
};
console.log("descriptor on source", Object.getOwnPropertyDescriptor(source, "prop"));
var target = Object.assign({}, source);
console.log("descriptor on target", Object.getOwnPropertyDescriptor(target, "prop"));

要在 中定义该属性,使用 defineProperty

To define that property on this inside Class, use defineProperty:

function Class() {
  Object.defineProperty(this, "prop", {
    get() { console.log('call get') },
    set(v) { console.log('call set') },
  });
}
var c = new Class();
console.log(c.prop); // => 'call get', undefined
c.prop = 'change'; // => 'call set'
console.log(c.prop); // => 'call get', undefined

这篇关于Object.assign构造函数中的getter和setter的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

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