javascript - 如何在 javascript/vuejs 中复制对象

Question

我正在使用 js 对象，可以说:

items: [{text: 'text1', active: true},
{text: 'text1', active: true},
{text: 'text1', active: true}]

我想复制对象并在计算属性中对它们进行一些更改，如下所示:

computed: {
   copyAndChange() {
      var itemsCopy = []
      itemsCopy = this.items
      for (var i=0; i<itemsCopy.length; i++) {
         itemsCopy[i].text = "something"
         console.log('text from items: ' + this.item[i])
         console.log('text from itemsCopy: ' + itemsCopy[i])
      }
      return itemsCopy
   }
}

此代码在控制台中显示:

text from items: something
text from itemsCopy: something
text from items: something
text from itemsCopy: something
text from items: something
text from itemsCopy: something

(？)为什么？我预计:

This code gives me in console:
text from items: text1
text from itemsCopy: something
text from items: text1
text from itemsCopy: something
text from items: text1
text from itemsCopy: something

这里出了什么问题？

Answer 1

您没有创建副本。您将对 this.items 的引用分配给 itemsCopy 数组。因此，您稍后会改变同一个数组。

创建副本:

itemsCopy = this.items.slice();

同样的问题也适用于数组中的每个对象。在循环中，创建对象的副本:

var obj = Object.assign({}, itemsCopy[i]);
obj.text = "something";
itemsCopy[i] = obj;  //replace the old obj with the new modified one.

<小时/>

演示:

var items = [
  {text: 'text1', active: true},
  {text: 'text1', active: true},
  {text: 'text1', active: true}
];

function copyAndChange() {
  var itemsCopy = []
  itemsCopy = items.slice();
  for (var i=0; i<itemsCopy.length; i++) {
    var obj = Object.assign({}, itemsCopy[i]);
    obj.text = "something";
    itemsCopy[i] = obj;  //replace the old obj with the new modified one.
    console.log('text from items: ' + items[i].text)
    console.log('text from itemsCopy: ' + itemsCopy[i].text)
  }
  return itemsCopy
}

copyAndChange();