TypeScript singleton pattern All In One

TypeScript singleton pattern All In One

singleton pattern / 单例模式

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2022-03-31
 * @modified
 *
 * @description
 * @augments
 * @example
 * @link
 *
 */

const log = console.log;

// 只能创建单个类的实例
class Human {
    // 私有构造器函数，不可以通过 new 创建类的实例
    constructor(name) {
        this.name = name;
    }
    // public static createInstance() {
    static createInstance(name) {
        if (!Human.isExist) {
            Human.isExist = true;
            this.instance = new Human(name);
        }
        else {
            // ignore
        }
        return this.instance;
    }
}
Human.isExist = false;
// const human = new Human('eric');
// Constructor of class 'Human' is private and only accessible within the class declaration.ts(2673)
const h1 = Human.createInstance('abc');
const h2 = Human.createInstance('xyz');
log('h1 name', h1.name);
log('h2 name', h2.name);
// h1 name abc
// h2 name abc

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2022-03-31
 * @modified
 *
 * @description
 * @augments
 * @example
 * @link
 *
 */

const log = console.log;

class Human {
    // 私有构造器函数，不可以通过 new 创建类的实例
    constructor(name) {
        this.name = name;
    }
    // public static createInstance() {
    static createInstance(name) {
        if (!Human.isExist) {
            Human.isExist = true;
            Human.instance = new Human(name);
        }
        else {
            // ignore
        }
        return Human.instance;
    }
}
Human.isExist = false;
// const human = new Human('eric');
// Constructor of class 'Human' is private and only accessible within the class declaration.ts(2673)
const h1 = Human.createInstance('abc');
const h2 = Human.createInstance('xyz');
log('h1 name', h1.name);
log('h2 name', h2.name);
// h1 name abc
// h2 name abc

demo

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2022-03-31
 * @modified
 *
 * @description
 * @augments
 * @example
 * @link
 *
 */

const log = console.log;

class Person {
  // public name: string;
  name: string
  constructor(name: string) {
    this.name = name;
  }
}

// 可以创建多个不同的类的实例
const p1 = new Person('abc');
const p2 = new Person('xyz');


// singleton pattern 单例模式
// 只能创建单个类的实例

class Human {
  private static isExist: boolean = false;
  private static instance: Human;
  // public name: string
  name: string
  // 私有构造器函数，不可以通过 new 创建类的实例
  private constructor(name: string) {
    this.name = name;
  }
  // public static createInstance() {
  static createInstance(name: string) {
    if (!Human.isExist) {
      Human.isExist = true;
      Human.instance = new Human(name);
    } else {
      // ignore
    }
    return Human.instance;
  }
}

// const human = new Human('eric');
// Constructor of class 'Human' is private and only accessible within the class declaration.ts(2673)

const h1 = Human.createInstance('abc');
const h2 = Human.createInstance('xyz');

log('h1 name', h1.name);
log('h2 name', h2.name);

export {}

"use strict";
/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2022-03-31
 * @modified
 *
 * @description
 * @augments
 * @example
 * @link
 *
 */
const log = console.log;
class Person {
    constructor(name) {
        this.name = name;
    }
}
// 可以创建多个不同的类的实例
const p1 = new Person('abc');
const p2 = new Person('xyz');
// singleton pattern 单例模式
// 只能创建单个类的实例
class Human {
    // 私有构造器函数，不可以通过 new 创建类的实例
    constructor(name) {
        this.name = name;
    }
    // public static createInstance() {
    static createInstance(name) {
        if (!Human.isExist) {
            Human.isExist = true;
            Human.instance = new Human(name);
        }
        else {
            // ignore
        }
        return Human.instance;
    }
}
Human.isExist = false;
// const human = new Human('eric');
// Constructor of class 'Human' is private and only accessible within the class declaration.ts(2673)
const h1 = Human.createInstance('abc');
const h2 = Human.createInstance('xyz');
log('h1 name', h1.name);
log('h2 name', h2.name);

export {};

https://www.typescriptlang.org/play?#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-qJhgCwEwDj8ateQjjUSHXGzA0SZdrvA7qWi3tXvaPp8aN9fusKYCpqDK7N5ktPe6oisjCYzNIKra0zcl1Nj56z67Lymb-cy087yuvRwoDcAIQZraLQ+n6cBft+lrWsBoH+v8lwQDG35AaIIFXqm0D1JSNIoXOiTsu8UDAlAEBRtAy7fjmiAsKIDC5N+u4rsYsAgEqUGZmhr6ITuYLYDmnI0NBYaDjhQmMsMKBihKADCU7wFcsqMHQv7dL0-QMihDJev0jqIC6E62pYMSCKoUAUMgaZ9IgSzQFSiBfGMtDQKp5ohKp8AejELTJDcVgAGwAOzOM8ZRTlANDkvUKEtE+F7oTeTIslJAnclFQkxcYz7xRAgoilJmDtIyEUFhADIADThe4G74VghUMjQ3L3OV4VWNVEAEZg6TKAw2jjKCQA

class Human {
  // 初始化
  private static isExist: boolean = false;
  // 未初始化
  private static instance: Human;
  // public name: string
  name: string
  // 私有构造器函数，不可以通过 new 创建类的实例
  private constructor(name: string) {
    this.name = name;
  }
  // public static createInstance() {
  static createInstance(name: string) {
    if (!Human.isExist) {
      Human.isExist = true;
      // this.instance = new Human(name);
      Human.instance = new Human(name);
    } else {
      // ignore
    }
    console.log(this.instance === Human.instance);
    // return this.instance;
    return Human.instance;
  }
}

// const human = new Human('eric');
// Constructor of class 'Human' is private and only accessible within the class declaration.ts(2673)

const h1 = Human.createInstance('abc');
const h2 = Human.createInstance('xyz');

log('h1 name', h1.name);
log('h2 name', h2.name);

js singleton pattern

ES5 / ES6

// IIFE
var Singleton = (function () {
    var instance;
    // 闭包 closure
    function createInstance() {
        var object = new Object("I am the instance");
        return object;
    }
    return {
        // 单例模式 getInstance
        getInstance: function () {
            if (!instance) {
                // 实例化 1 次
                instance = createInstance();
            }
            return instance;
        }
    };
})();

function run() {
    var instance1 = Singleton.getInstance();
    var instance2 = Singleton.getInstance();
    console.log("Same instance? " + (instance1 === instance2));
}

js custom new keyword

// 1. create object, allocate memory

// 2. bind this

// 3. bind prototype

// 4. return object

function CustomNew (Func, args) {
   // const obj = Object.create(func);
   const obj = {};
   // const obj = Object.assign({});
   Func.call(obj, args);
   // Func.call(obj, ...args);
   // Func.apply(obj, [...args]);
   obj.__proto__ = Func.prototype;
   return obj;
}

https://www.cnblogs.com/xgqfrms/tag/new

https://www.cnblogs.com/xgqfrms/p/15998513.html

https://www.cnblogs.com/xgqfrms/p/13717265.html

refs

https://www.typescriptlang.org/play

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