{} 对象与自定义构造函数之间的隐藏类和等效性 (v8) [英] Hidden classes and equivalence between {} object vs. custom constructor (v8)

问题描述

鉴于这篇文章:

http://richardartoul.github.io/jekyll/update/2015/04/26/hidden-classes.html

如果您创建一个构造函数，例如:

If you create a constructor such as:

function Point(x,y) {
  this.x = x;
  this.y = y;
}

然后这样做:

var obj1 = new Point(1,2);
var obj2 = new Point(3,4);

obj1.a = 5;
obj1.b = 10;

obj2.b = 10;
obj2.a = 5;

意味着您在幕后进行了某种性能优化.

means you get some sort of performance optimizations under the hood.

我想知道，如果你只是这样做:

I'm wondering though, if you just do this instead:

var obj1 = { a: 5, b: 10 }
var obj2 = { b: 10, a: 5 }

如果您对数千个对象遵循该模式，或者为每个 var objn 实例创建一个新的隐藏类，您是否会获得相同的性能优化.

Will you get the same performance optimizations if you follow that pattern for thousands of objects, or is a new hidden class created for each var objn instance.

基本上想知道是否需要使用构造函数来获得这种性能优化.

Basically wondering if it's required to use a constructor function to get this performance optimization.

推荐答案

正如文章在其摘要中所说:

As the article says in its summary:

始终以相同的顺序实例化您的对象属性，以便可以共享隐藏的类和随后优化的代码.

Always instantiate your object properties in the same order so that hidden classes, and subsequently optimized code, can be shared.

在您的替代示例中 var obj1 = { a: 5, b: 10 };var obj2 = { b: 10, a: 5 }，属性显然不是按照相同的顺序添加的，所以隐藏的类无法共享.

In your alternative example var obj1 = { a: 5, b: 10 }; var obj2 = { b: 10, a: 5 }, the properties are clearly not added in the same order, so the hidden classes cannot be shared.

您不必使用构造函数本身，但使用构造函数是确保获得所需性能的最简单方法.(这通常也被认为是符合人体工程学和良好的编码习惯.)

You don't have to use a constructor per se, but using a constructor is the easiest way to ensure that you're getting the performance you want. (It is also generally considered ergonomic and good coding practice.)

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