如果你想使用类:

class Singleton {
  constructor(name, age) {
    this.name = name;
    this.age = age;
    if(this.constructor.instance)
      return this.constructor.instance;
    this.constructor.instance = this;
  }
}
let x = new Singleton('s', 1);
let y = new Singleton('k', 2);

以上的输出将是:

console.log(x.name, x.age, y.name, y.age) // s 1 s 1

另一种使用函数编写Singleton的方法

function AnotherSingleton (name,age) {
  this.name = name;
  this.age = age;
  if(this.constructor.instance)
    return this.constructor.instance;
  this.constructor.instance = this;
}

let a = new AnotherSingleton('s', 1);
let b = new AnotherSingleton('k', 2);

以上的输出将是:

console.log(a.name, a.age, b.name, b.age) // s 1 s 1

我需要几个单人间:

延迟初始化 初始参数

这就是我想到的:

createSingleton ('a', 'add', [1, 2]);
console.log(a);

function createSingleton (name, construct, args) {
    window[name] = {};
    window[construct].apply(window[name], args);
    window[construct] = null;
}

function add (a, b) {
    this.a = a;
    this.b = b;
    this.sum = a + b;
}

args必须是Array，所以如果你有空变量，只需要传入[] 我在函数中使用了window对象，但我本可以传入一个参数来创建自己的作用域 name和构造参数只是字符串，以便window[]工作，但有一些简单的类型检查，window.name和window.name。构造也是可能的。

单例模式:

确保一个类只有一个实例，并提供对它的全局访问点。

单例模式将特定对象的实例数量限制为一个。这个单一实例称为单例。

定义返回唯一实例的getInstance()。 负责创建和管理实例对象。

单例对象被实现为一个即时匿名函数。函数立即执行，将它括在括号中，然后再加上两个括号。它被称为匿名，因为它没有名字。

示例程序

var Singleton = (function () { var instance; function createInstance() { var object = new Object("I am the instance"); return object; } return { getInstance: function () { if (!instance) { instance = createInstance(); } return instance; } }; })(); function run() { var instance1 = Singleton.getInstance(); var instance2 = Singleton.getInstance(); alert("Same instance? " + (instance1 === instance2)); } run()

JavaScript中的单例是使用模块模式和闭包实现的。

下面的代码是不言自明的

// Singleton example.
var singleton = (function() {
  var instance;

  function init() {
    var privateVar1 = "this is a private variable";
    var privateVar2 = "another var";

    function pubMethod() {
      // Accessing private variables from inside.
      console.log(this.privateVar1);
      console.log(this.privateVar2);
      console.log("inside of a public method");
    };
  }

  function getInstance() {
    if (!instance) {
      instance = init();
    }
    return instance;
  };

  return {
    getInstance: getInstance
  }
})();

var obj1 = singleton.getInstance();
var obj2 = singleton.getInstance();

console.log(obj1 === obj2); // Check for type and value.

let MySingleton = (function () {
  var _instance
  function init() {
    if(!_instance) {
      _instance = { $knew: 1 }
    }
    return _instance
  }
  let publicAPIs = {
    getInstance: function() {
      return init()
    }
  }
  // this prevents customize the MySingleton, like MySingleton.x = 1
  Object.freeze(publicAPIs) 
  // this prevents customize the MySingleton.getInstance(), like MySingleton.getInstance().x = 1
  Object.freeze(publicAPIs.getInstance())
  return publicAPIs
})();

下面是我实现单例模式的演练片段。这是我在面试过程中想到的，我觉得我应该在某个地方捕捉到这一点。

/*************************************************
 *     SINGLETON PATTERN IMPLEMENTATION          *
 *************************************************/

// Since there aren't any classes in JavaScript, every object
// is technically a singleton if you don't inherit from it
// or copy from it.
var single = {};


// Singleton Implementations
//
// Declaring as a global object...you are being judged!

var Logger = function() {
  // global_log is/will be defined in the GLOBAL scope here
  if(typeof global_log === 'undefined'){
    global_log = this;
  }
  return global_log;
};


// The below 'fix' solves the GLOABL variable problem, but
// the log_instance is publicly available and thus can be
// tampered with.
function Logger() {
  if(typeof Logger.log_instance === 'undefined') {
    Logger.log_instance = this;
  }

  return Logger.log_instance;
};


// The correct way to do it to give it a closure!

function logFactory() {
  var log_instance; // Private instance
  var _initLog = function() { // Private init method
    log_instance = 'initialized';
    console.log("logger initialized!")
  }
  return {
    getLog : function(){ // The 'privileged' method
      if(typeof log_instance === 'undefined') {
        _initLog();
      }
      return log_instance;
    }
  };
}


/***** TEST CODE ************************************************

// Using the Logger singleton
var logger = logFactory(); // Did I just give LogFactory a closure?

// Create an instance of the logger
var a = logger.getLog();

// Do some work
// Get another instance of the logger
var b = logger.getLog();

// Check if the two logger instances are same
console.log(a === b); // true
*******************************************************************/

同样可以在我的主旨页面上找到。