为什么更新一个对象中的属性会更改另一个对象？ [英] Why does updating properties in one object change another object?

问题描述

我通过ajax将JSON数据加载到对象，将该对象复制到新对象（initData和newData）。当我改变newData的属性时，initData的属性也改变。为什么会发生这种情况？

I'm loading JSON data into an object via ajax, copying that object to new objects (initData and newData). When I change the property of newData, the property of initData also changes. Why is this happening?

var initData = {};
var newData = {};    

function load_data(NDB_No){
    $.getJSON(('scripts/jsonencode.php?q=' + NDB_No), function(data) {

        for (prop in data){
            initData[prop] = data[prop];
            newData[prop] = data[prop];
        }

    console.log('init data: ' + initData.properties.Protein); // "init data: 0.259"
    console.log('new data: ' + newData.properties.Protein); // "new data: 0.259"

     var n = parseFloat(newData.properties.Protein);
     newData.properties.Protein = n+1;

    console.log('init data: ' + initData.properties.Protein + 'new data: ' + newData.properties.Protein); 
    // "init data: 1.259 new data: 1.259"
    // why are these the same when I only updated newData object?


    });


}

推荐答案

它看起来像 data [prop] 是一个对象（因为你以后指的是 newData.properties.Protein ）。对象总是通过引用传递，而变量只是一个指向它的指针。

It looks like data[prop] is an object (since you are later referring to newData.properties.Protein). Objects are always passed by reference, with the variable just being a pointer to it.

由于你首先获得JSON，你的对象是JSON能力的，因此您可以使用它来克隆对象：

Since you're getting JSON in the first place, your object is JSON-able, so you can use that to "clone" the object:

$.getJSON(...,function(data) {
    initData = JSON.parse(JSON.stringify(data));
    newData = JSON.parse(JSON.stringify(data));
});

这将确保对象是独立的。还有其他方法可以做到这一点，但这个避免手动递归通过使用内置的方法（总是更快）

This will ensure that the objects are separate. There are other ways to do this, but this one avoids the manual recursion by using built-in methods (always faster)

这篇关于为什么更新一个对象中的属性会更改另一个对象？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！