为什么更新一个对象的属性会改变另一个对象?

问题描述

我正在通过 ajax 将 JSON 数据加载到一个对象中，将该对象复制到新对象(initData 和 newData).当我更改 newData 的属性时，initData 的属性也会更改.为什么会这样?

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

看起来 data[prop] 是一个对象(因为你后面提到 newData.properties.Protein).对象总是通过引用传递，变量只是指向它的指针.

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