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javascript – 新手：需要一些关于这个js代码的解释

2019-08-01 JavaScript 前端之家

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@H_404_0@

我正在学习javascript,我已经阅读了somewhere以下代码：

if (typeof Object.create !== 'function') {
    Object.create = function (o) {
        function F() {}
        F.prototype = o;
        return new F();
    };
}
newObject = Object.create(oldObject);

我知道Object.create函数返回一个新对象,该对象继承了作为参数传递给Object.create函数的对象’o’.但是,我不明白这是什么意思呢？我的意思是,即使Object.create函数返回一个新对象,但新对象和旧对象没有区别.即使是新对象继承旧对象,也没有在新对象中定义新方法.那么,在什么情况下我们需要上面的代码来获取新对象？

最佳答案

其他几个答案已经在解释这个问题,但我想补充一个例子：

var steve = { eyes: blue,length: 180,weight: 65 };
var stevesClone = Object.create(steve);

// This prints "eyes blue,length 180,weight 65"
for (var property in stevesClone) {
  console.log(property,stevesClone[property]);
}

// We can change stevesClone without changing steve:
stevesClone.eyes = "green";
stevesClone.girlfriend = "amy";


// This prints "eyes green,weight 65,girlfriend amy"
for (var property in stevesClone) {
  console.log(property,stevesClone[property]);
}

// But if we alter steve,those properties will affect stevesClone as well
// unless they have also been assigned to stevesClone directly:
steve.father = "carl";
steve.eyes = "red";

// So,the clone got steves father carl through inheritance,but keeps his
// green eyes since those were assigned directly to him.

// This prints "eyes green,girlfriend amy,father carl"
for (var property in stevesClone) {
  console.log(property,stevesClone[property]);
}

Object.create从现有对象创建一个新对象,并使用原型链来维护它们之间的关系.如果克隆本身没有这些属性,那么来自stevesClone的任何内容都会传播到史蒂夫.因此,对steve的更改可能会影响克隆,但反之亦然.

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