javascript - JS 模块模式 = 缓存/更好的性能？

Question

我刚刚读了这篇文章http://javascriptweblog.wordpress.com/2011/05/31/a-fresh-look-at-javascript-mixins/ .

在标题为“#4 添加缓存”的部分中，它说:

By forming a closure around the mixins we can cache the results of the initial definition run and the performance implications are outstanding.

我不明白它是如何工作的——在这里使用模块模式如何导致代码的更快/缓存版本？

Answer 1

基本上，在不使用闭包的情况下，mixin 函数将在每个使用 mixin 的时间。通过创建闭包，每个函数都将创建一次，mixin 每次创建时都会引用这些函数叫。由于 mixin 不必每次都重新创建这些函数运行速度更快。

没有关闭

var asRectangle = function() {
  // every time this function is called, these three functions are created
  // from scratch, slowing down execution time
  this.area = function() {
    return this.length * this.width;
  }
  this.grow = function() {
    this.length++, this.width++;
  }
  this.shrink = function() {
    this.length--, this.width--;
  }
})();

关闭

var asRectangle = (function() {
  // these functions are 'cached' in the closure
  function area() {
    return this.length * this.width;
  }
  function grow() {
    this.length++, this.width++;
  }
  function shrink() {
    this.length--, this.width--;
  }

  // this function is set to asRectangle.  it references the above functions
  // every time it is called without having to create new ones
  return function() {
    this.area = area;
    this.grow = grow;
    this.shrink = shrink;
    return this;
  };
})();