带Browserify / CommonJS的单例模式 [英] Singleton pattern with Browserify/CommonJS

问题描述

尝试使用Browserify在CommonJS模块中实现单例模式。到目前为止：

Trying to implement the singleton pattern within CommonJS modules, using Browserify. So far:

// foo.js

// foo.js

var instance = null;

var Foo = function(){
    if(instance){
        return instance;
    }
    this.num = 0;
    return instance = new Foo();
}

Foo.prototype.adder = function(){
    this.num++;
};

module.exports = Foo();

// main.js

// main.js

var foo = require('./foo.js');
console.log(foo.num); // should be 0
foo.adder(); // should be 1
var bar = require('./foo.js');
console.log(bar.num); // like to think it'd be 1, not 0

第一个问题是我得到一个<当我在浏览器中加载生成的JS文件时，超出了code>超出最大调用堆栈数的错误，但是第二，我是否正确地解决了这个问题？

First problem is that I get a maximum call stack exceeded error when I load the built JS file in the browser, but secondly, am I approaching this correctly? Is this possible?

推荐答案

第一个问题是我得到最大调用堆栈超出错误

First problem is that I get a maximum call stack exceeded error

好吧，这来自于您的 Foo 函数递归调用新的Foo …

Well, that comes from your Foo function recursively calling new Foo…

但是第二，我是否正确地解决了这个问题？

but secondly, am I approaching this correctly?

否。对于单例来说，您不需要带有构造函数和原型的类-永远只有一个实例。只需创建一个对象，最简单的方法就是使用文字，然后返回该对象：

No. For singletons, you don't need a "class" with a constructor and a prototype - there will only ever be one instance. Simply create one object, most easily with a literal, and return that:

module.exports = {
    num: 0,
    adder: function(){
        this.num++;
    }
};

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