当不再需要变量时将变量设置为 null 是一种好习惯吗? [英] Is it good practice to set variables to null when they are no longer needed?

问题描述

我已经看到在函数的末尾将 javascript 值设置为 null.这样做是为了减少内存使用，还是只是为了防止意外使用在其他地方?

I have seen javascript values set to null at the end of a function. Is this done to reduce memory usage or just to prevent accidental usage elsewhere?

是否有这样做的好例子.如果是，什么时候?

Is there a good case for doing this. If so when?

var myValue;
.
.
.
myValue = null;

推荐答案

在函数结束时将局部变量设置为 null 没有任何区别，因为它会从无论如何返回时堆栈.

It wouldn't make any difference setting a local variable to null at the end of the function because it would be removed from the stack when it returns anyway.

但是，在闭包内部，变量将不会被释放.

However, inside of a closure, the variable will not be deallocated.

var fn = function() {

   var local = 0;

   return function() {
      console.log(++local);
   }

}

var returned = fn();

returned(); // 1
returned(); // 2

jsFiddle.

当内部函数返回时，外部变量的作用域将继续存在，可供返回的内部函数访问.

When the inner function is returned, the outer variable's scope will live on, accessible to the returned inner function.

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