JavaScript assigns an associative array A to B, and then changes the contents of a, why does B change as well?

JS:var a = {"Client":"jQuery","Server":"PHP"};var b = a;a["New"] = "Element";console.log(b);// 输出 Object { Client="jQuery",  Server="PHP",  New="Element"}PHP例程1:$a = array('Client'=>'jQuery','Server'=>'PHP');$b = $a;$a['New'] = 'Element';var_export($b);//输出 array('Client'=>'jQuery','Server'=>'PHP')PHP例程2:$a = array('Client'=>'jQuery','Server'=>'PHP');$b = &$a; //引用赋值$a['New'] = 'Element';var_export($b);//输出 array('Client'=>'jQuery','Server'=>'PHP','New'=>'Element')

JavaScript assigns an associative array A to B, and then changes the contents of a, why does B change as well?

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JS:var a = {"Client":"jQuery","Server":"PHP"};var b = a;a["New"] = "Element";console.log(b);// 输出 Object { Client="jQuery",  Server="PHP",  New="Element"}PHP例程1:$a = array('Client'=>'jQuery','Server'=>'PHP');$b = $a;$a['New'] = 'Element';var_export($b);//输出 array('Client'=>'jQuery','Server'=>'PHP')PHP例程2:$a = array('Client'=>'jQuery','Server'=>'PHP');$b = &$a; //引用赋值$a['New'] = 'Element';var_export($b);//输出 array('Client'=>'jQuery','Server'=>'PHP','New'=>'Element')

JavaScript assigns an associative array A to B, and then changes the contents of a, why does B change as well?

For an array of such non-trivial types (String, Integer, Boolean), your assignment is equivalent to the copy of the address, that is, a, B occupies the same address. So change the b,a will also change, in essence A, B is a thing.

This answer is detailed here, the array belongs to the reference type value, stored in the heap. Https://www.zhihu.com/questio ...

Online to see some people say that when the assignment in JS, the original type (such as String) is a copy of the value, reference type (such as associative array) is a copy reference.

var a = {"Client":"jQuery","Server":"PHP"};var b = JSON.stringify(a); //转成字符串后赋值a["New"] = "Element";console.log(JSON.parse(b)); //使用时转回关联数组(对象)//输出 Object { Client="jQuery",  Server="PHP"}IE8不支持JSON.parse和JSON.stringify,需要引入json2.js:http://www.json.org/js.htmlhttps://github.com/douglascrockford/JSON-js/blob/master/json2.jsIE9以下版本:
  
   

The sense JS array is not PHP flexible, PHP support with & Declaration reference assignment, PHP array is "Copy on write":

echo round(memory_get_usage()/(1024*1024))."MB\n"; //0MB$a = file('/home/eechen/note.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);echo round(memory_get_usage()/(1024*1024))."MB\n"; //9MB$b = $a;echo round(memory_get_usage()/(1024*1024))."MB\n"; //9MB(赋值后内存没有变化)$b['new'] = 'element';echo round(memory_get_usage()/(1024*1024))."MB\n"; //14MB(修改后内存发生变化,即写时复制)

Because A and B point to the same number of groups AH.

If you want to do not change, the object is converted to a string, and then converted back to the object, is two different objects. Directly with the words, is actually a. The positive solution has been given upstairs.

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