在一种情况下是相同的对象，在另一种情况下是不同的对象？

Question

我想弄清楚下面处理将一个对象复制到另一个对象的代码中发生了什么。在某些情况下，它们就像同一个对象一样，改变一个就会改变另一个。我发现了很多关于 javascript 对象如何通过引用复制的帖子，因此它们实际上是同一个对象。例如，来自 http://www.w3schools.com/js/js_object_definition.asp:

 var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"} 
 var x = person;  // This will not create a copy of person. 
 x.age = 10; // This will change both x.age and person.age

 The object x is not a copy of person. It is person. Both x and person
 is the same object. Any changes to x will also change person, because
 x and person are the same object.

不过，我也发现了对象看起来是独立对象的情况。它怎么能在一种情况下表现得像同一个对象，而在另一种情况下表现得像不同的对象呢？我将不胜感激：

示例：http://codepen.io/gratiafide/pen/yagQGr?editors=1010#0

HTML:

<div id="app">
  <my-component>
  </my-component>
</div>

JS:

  var MyComponent = Vue.extend({
  template: '<div v-on:click="test()" class="red">1.  Click here to copy the name object to message and change the value of name to see if the value of message gets changed also.  (It does not).</div>  message: {{ message | json}} <br> name: {{ name | json}}<div v-on:click="test2()" class="red">2.  Now click here to see if updating  the name object also changes the message object.  It does!  Why here and not in #1?</div><div v-on:click="test3()" class="red">3.  Click here to see yet another way of updating the name object also changes the message object. Why here and not in #1?</div>',

  data: function () {
    return { 
    message: {},
    name: {}
    }
  },

  ready: function(){
    this.message = {};
  },
  methods: {
    test: function(){
       this.message = {'t1':"m1"};
       this.name = this.message;  
       this.name = {'t2':"m2"};  
    },
    test2: function(){
       this.message = {'t1':"m1"};
       this.name = this.message;  
       for (var key in this.name) {
                this.name[key] = '';
            }  
    },
    test3: function(){
       this.message = {'t1':"m1"};
       this.name = this.message;  
       Vue.set(this.name, 't1', 'm2');
    }
  }
});

Vue.component('my-component', MyComponent);

new Vue({
  el: '#app'
});

CSS:

@import url(https://fonts.googleapis.com/css?family=Open+Sans);

.red{
  color:red;  
}

body {
  font-family: 'Open Sans', sans-serif;
  background: rgba(0,0,0,.5);
  margin: 0;
}

#app {
  width: 500px;
  margin: 0 auto;
  padding: 10px 20px;
  background: rgba(255,255,255,.9);
}

Answer 1

基本上，你问的是这三者的区别：

this.message = {'t1':"m1"};
this.name = this.message;  

#1:
this.name = {'t2':"m2"};  

#2
for (var key in this.name) {
  this.name[key] = '';
}  

#3
Vue.set(this.name, 't1', 'm2');

在第一种情况下，您不会更改 this.message，因为您正在将一个全新的对象分配给 this.name。这个新对象 ({'t2':"m2"}) 与 this.message.

完全无关

也许您 trying/thinking 所做的是：

this.name.t2 = "m2";

这与#2 和#3 相同，影响 this.message，因为 this.name 仍然指的是同一个对象。

要从另一个对象向现有对象分配新属性，您可以在支持此功能的浏览器中使用Object.assign：

Object.assign(this.name, {'t2':"m2"});

Answer 2

有两种类型的变量，值和引用。所有基元（即字符串、数字和布尔值）都按值存储，其他所有内容都按引用存储并且可以具有属性。

var a,b;
a={c:1};
b=a;
console.log (b===a); // true;

b={c:1}; // note that b is now being assigned a new reference.
console.log (b===a); // false;

a=b; // now a is being assigned the reference of b.
console.log (b===a); // true;

a.c=2; //note that it is the property of a (c) got changed, not a itself.
console.log (b===a); // true;

a.a = a; //now a has a property (a) that stores the reference of a.
console.log(a === a.a);
console.log(a.a === a.a.a);
console.log(a.a === a.a.a.a.a.a.a.a.a);
a.a.a.a.a.a.a.a.a.a.a.c = 10;
console.log(a.c)//10;

有不同的方法来声明变量，但这不是问题的范围。

在一种情况下是相同的对象，在另一种情况下是不同的对象？

Same object in one case, different object in another?

javascript

vue.js

vue-component