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javascript:最佳单例模式[duplicate]

design-patterns singleton javascript

Kaze no Koe · 技术社区 · 16 年前

可能重复:
Simplest/Cleanest way to implement singleton in JavaScript?

我将这个模式用于单重态,在这个例子中,单重态是planetearth:

var NAMESPACE = function () {

    var privateFunction1 = function () {
        privateFunction2();
    };

    var privateFunction2 = function () {
        alert('I\'m private!');
    };

    var Constructors = {};

    Constructors.PlanetEarth = function () {
        privateFunction1();
        privateFunction2();
    };

    Constructors.PlanetEarth.prototype = {
        someMethod: function () {
            if (console && console.log) {
                console.log('some method');             
            }
        }
    };

    Constructors.Person = function (name, address) {
        this.name = name;
        this.address = address;
    };

    Constructors.Person.prototype = {
        walk: function () {
            alert('STOMP!');
        }
    };

    return {
        Person: Constructors.Person, // there can be many
        PlanetEarth: new Constructors.PlanetEarth() // there can only be one!
    };

}();

自从 行星地球 构造函数仍然是私有的,只能有一个。

现在,有人告诉我,这种自我烹饪的东西并不是最好的,主要是因为我没有受过学术教育,我倾向于用愚蠢的方式解决问题。作为一个 更好的 替代我的方法,其中 更好的 定义为 风格更好和/或更强大 ?

4 回复 | 直到 7 年前

154

tomasdev 7 年前

(1)更新2019:ES7版本

class Singleton {
    static instance;

    constructor() {
        if (instance) {
            return instance;
        }

        this.instance = this;
    }

    foo() {
        // ...
    }
}

console.log(new Singleton() === new Singleton());

(2)ES6版本

class Singleton {
    constructor() {
        const instance = this.constructor.instance;
        if (instance) {
            return instance;
        }

        this.constructor.instance = this;
    }

    foo() {
        // ...
    }
}

console.log(new Singleton() === new Singleton());

找到的最佳解决方案: http://code.google.com/p/jslibs/wiki/JavascriptTips#Singleton_pattern

function MySingletonClass () {

  if (arguments.callee._singletonInstance) {
    return arguments.callee._singletonInstance;
  }

  arguments.callee._singletonInstance = this;

  this.Foo = function () {
    // ...
  };
}

var a = new MySingletonClass();
var b = MySingletonClass();
console.log( a === b ); // prints: true

对于那些想要严格版本的人:

(function (global) {
  "use strict";
  var MySingletonClass = function () {

    if (MySingletonClass.prototype._singletonInstance) {
      return MySingletonClass.prototype._singletonInstance;
    }

    MySingletonClass.prototype._singletonInstance = this;

    this.Foo = function() {
      // ...
    };
  };

var a = new MySingletonClass();
var b = MySingletonClass();
global.result = a === b;

} (window));

console.log(result);

bobince 16 年前

为什么要为单个对象使用构造函数和原型?

以上相当于:

var earth= {
    someMethod: function () {
        if (console && console.log)
            console.log('some method');                             
    }
};
privateFunction1();
privateFunction2();

return {
    Person: Constructors.Person,
    PlanetEarth: earth
};

Community Mohan Dere 9 年前

Extending 上面的文章由tom撰写,如果您需要一个类类型声明并使用变量访问singleton实例,下面的代码可能会有帮助。我喜欢这个符号,因为代码有点自我指导。

function SingletonClass(){
    if ( arguments.callee.instance )
        return arguments.callee.instance;
    arguments.callee.instance = this;
}


SingletonClass.getInstance = function() {
    var singletonClass = new SingletonClass();
    return singletonClass;
};

要访问singleton,您需要

var singleTon = SingletonClass.getInstance();

Alain Lecluse 15 年前

function SingletonClass() 
{
    // demo variable
    var names = [];

    // instance of the singleton
    this.singletonInstance = null;

    // Get the instance of the SingletonClass
    // If there is no instance in this.singletonInstance, instanciate one
    var getInstance = function() {
        if (!this.singletonInstance) {
            // create a instance
            this.singletonInstance = createInstance();
        }

        // return the instance of the singletonClass
        return this.singletonInstance;
    }

    // function for the creation of the SingletonClass class
    var createInstance = function() {

        // public methodes
        return {
            add : function(name) {
                names.push(name);
            },
            names : function() {
                return names;
            }
        }
    }

    // wen constructed the getInstance is automaticly called and return the SingletonClass instance 
    return getInstance();
}

var obj1 = new SingletonClass();
obj1.add("Jim");
console.log(obj1.names());
// prints: ["Jim"]

var obj2 = new SingletonClass();
obj2.add("Ralph");
console.log(obj1.names());
// Ralph is added to the singleton instance and there for also acceseble by obj1
// prints: ["Jim", "Ralph"]
console.log(obj2.names());
// prints: ["Jim", "Ralph"]

obj1.add("Bart");
console.log(obj2.names());
// prints: ["Jim", "Ralph", "Bart"]