修改JavaScript对象的副本会导致原始对象更改 [英] Modifying a copy of a JavaScript object is causing the original object to change

问题描述

我将 myObj 复制到 tempMyObj

var tempMyObj = myObj;

tempMyObj.entity 。我根据一些条件修改 tempMyObj.entity 。问题是如果我修改 tempMyObj.entity myObj.entity 也得到修改。

tempMyObj.entity is an array of objects. I am modifying tempMyObj.entity based on some conditions. The problem is if I modify tempMyObj.entity the myObj.entity is also getting modified.

for (j = 0; j < myObj.length; j++) {
    if (myObj[j].type == "TableShape") {
        var dupEntites = new Array();
        for (i = 0; i < myObj[j].entities.length; i++) {
            if (chk.value != myObj[j].entities[i].id) {
                var obj = {};
                obj.text = myObj[j].entities[i].text;
                obj.id = myObj[j].entities[i].id;
                dupEntites.push(obj);
            }
            else {
                if (chk.checked)
                {
                    var obj = {};
                    obj.text = myObj[j].entities[i].text;
                    obj.id = myObj[j].entities[i].id;
                    dupEntites.push(obj);
                }
            }
        }
        tempMyObj[j].entities = dupEntites;
    }
}

推荐答案

很清楚，你对语句 var tempMyObj = myObj; 有一些误解。

It is clear that you have some misconceptions of what the statement var tempMyObj = myObj; does.

在JavaScript对象通过引用传递和分配（更准确地说，引用的值），因此 tempMyObj myObj 都是对同一对象的引用。

In JavaScript objects are passed and assigned by reference (more accurately the value of a reference), so tempMyObj and myObj are both references to the same object.

这是一个简化的例子，可以帮助您直观地了解发生的情况

Here is a simplified illustration that may help you visualize what is happening

// [Object1]<--------- myObj

var tempMyObj = myObj;

// [Object1]<--------- myObj
//         ^ 
//         |
//         ----------- tempMyObj

您需要创建副本，如果您需要修改一个副本其他。

You need to create a copy if you need to modify one and not the other.

// [Object1]<--------- myObj

var tempMyObj = jQuery.extend(true, {}, myObj);

// [Object1]<--------- myObj
// [Object2]<--------- tempMyObj

以下是创建对象副本的几种方法：

由于你已经在使用jQuery：

Since you are already using jQuery:

var newObject = jQuery.extend(true, {}, myObj);

使用香草JavaScript

With vanilla JavaScript

function clone(obj) {
    if (null == obj || "object" != typeof obj) return obj;
    var copy = obj.constructor();
    for (var attr in obj) {
        if (obj.hasOwnProperty(attr)) copy[attr] = obj[attr];
    }
    return copy;
}

var newObject = clone(myObj);

查看这里和这里

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