JavaScript : Array assignment creates reference not copy-优快云博客

本文深入探讨了JavaScript中数组赋值时产生的引用问题而非值拷贝，并提供了几种有效的方法来实现数组的深拷贝，避免了因引用导致的意外数据变动。

29 May 2015

Consider we have an array var a = [1,2,3,4]; and we assign var b = a; then b not a copy of a, b is a pointer to a. So if you make any changes on b will have effect on a as well. Here is an example.

 
      var a = [1,2,3,4]; var b = a; var b.pop(); console.log(b); // [1, 2, 3] console.log(a); // [1, 2, 3]  
     

so if you really want a copy of a you need to use .slice method.

 
      var a = [1,2,3,4]; var b = a.slice(0); var b.pop(); console.log(b); // [1, 2, 3] console.log(a); // [1, 2, 3, 4]  
     

JavaScript doesn’t have a clone method for array, so if you really want, you can define yourself on Array but its not highly recommended.

 
      Array.prototype.clone = function(){ return this.slice(0) }  
     

Now you can call .clone on any Array type.

 
      var a = [1,2,3,4]; var b = a.clone(); var b.pop(); console.log(b); // [1, 2, 3] console.log(a); // [1, 2, 3, 4]  
     

I recommend to keep this in mind when ever you are dealing with JavaScript Array’s, else you might facing some unexpected behaviour and wonder why it happens.

Happy coding.

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