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        为什么更新一个对象的属性会改变另一个对象?

        时间:2023-10-02
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                  本文介绍了为什么更新一个对象的属性会改变另一个对象?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着跟版网的小编来一起学习吧!

                  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.

                  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.

                  由于您首先获取的是 JSON,因此您的对象是支持 JSON 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));
                  });
                  

                  这将确保对象是分开的.还有其他方法可以做到这一点,但是这种方法通过使用内置方法避免了手动递归(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的属性会改变另一个对象?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跟版网!

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