let Singleton = function ( name ) {
            this.name = name;
        }
        Singleton.instance = null;
        Singleton.prototype.getName  = function () {
            console.log( this.name )
        }
        Singleton.getInstance = function ( name ) {
            if( !this.instance ) {
                this.instance = new Singleton( name );
            }
            return this.instance;
        }
 
        let a = Singleton.getInstance('sk');
        let b = Singleton.getInstance('ss');
        console.log(a);
        console.log(a === b) // true

        let CreateDiv = function () {
            let instance ;
            let CreateDiv = function ( html ) {
                if( instance ) {
                    return instance;
                }
                this.html = html;
                this.init();
                return instance = this;
            }
            
            CreateDiv.prototype.init = function () {
                let element = document.createElement('div');
                element.innerHTML = this.html;
                document.body.appendChild(element);
            }
            return CreateDiv;
        }();
 
        let a = new CreateDiv('石頭山');
        let b = new CreateDiv('哈哈');
        console.log(a === b); // true 

        let CreateDiv = function ( html ) {
            this.html = html;
            this.init();
        }
        CreateDiv.prototype.init = function () {
            let div = document.createElement('div');
            div.innerHTML = this.html;
            document.body.appendChild(div);
        }
 
        let ProxySingletonCreateDiv = function () {
            let instance ;
            return function ( html ) {
                if( !instance ) {
                    instance = new CreateDiv( html );
                }
                return instance;
            }
        }();
        let a = new ProxySingletonCreateDiv('sven1');      
        let b = new ProxySingletonCreateDiv('sven2');
        console.log(a === b); // true

 let S = {
            name: '石頭山',
            getName() {
                console.log(this.name);
            }
        }

            let name = "石頭山";
            return {
                getName() {
                    return name;
                }
            }
        }

        // 寫一個(gè)通用的獲取單例的函數(shù) , fn 為執(zhí)行單次的函數(shù)
        let getSingle = function ( fn ) {
            let result;
            return function () {
                return result || ( result = fn.apply(this, arguments))
            }
        }
        // 綁定事件
        let bindEvent = function () {
            document.getElementById('div').addEventListener('click',()=>{
                console.log('我出現(xiàn)了')
            });
        }();
        // 無(wú)論渲染多少次，事件只綁定一次
        let render = function () {
            console.log('開(kāi)始渲染！');  
            getSingle(bindEvent)
        }
        render();
        render();
        render();