原生javascript单例模式的应用实例分析

<script>
let singleton = function (){
  function Map(width,height) {
    this.width = width;
    this.height = height;
  }
  let instance;
  return{
    getIntence : function(width,height){
      if(instance == undefined){
        instance = new Map(width,height);
      }else{
        instance.width = width;
        instance.height = height;
      }
      return instance;
    }
  }
}();
let m1 = singleton.getIntence(100,200);
let m2 = singleton.getIntence(200,300);
console.log(m1);//200 300
console.log(m2);//200 300
</script>

let mapSingleton = (function(){
  function Map(width,height,background){
    this.domObj = null;//地图的div
    this.moveBox = null;
    this.width = width;
    this.height = height;
    this.background = background;  
    this.enemyPlanes = [];//敌机数组
    this.myPlanes = [];//我方战机数组
    this.createUI();
    this.moveBg();
  }
  //853 600
  Map.prototype.createUI = function() {
    //1、地图的div
    this.domObj = document.createElement("div");
    this.domObj.style.cssText = `margin:20px auto;position: relative;width:${this.width}px;height:${this.height}px;overflow:hidden`;
    document.body.appendChild(this.domObj);
    //2、移动的div
    this.moveBox = document.createElement("div");
    this.moveBox.style.cssText = `position: absolute;
          top:-1106px;
          width: 480px;
          height: 1706px;`;
    this.domObj.appendChild(this.moveBox);        
    //3、图片
    for(var i=0;i<2;i++){
      let img01 = document.createElement("img");
      img01.src = this.background;
      img01.style.cssText = `display: block`;
      this.moveBox.appendChild(img01);
    }
    //4、积分板：
    this.scoreDom = document.createElement("div");
    this.scoreDom.style.cssText = "position:absolute;left:0px;top:0px;width:100px;height:35px;z-index:999";
    this.scoreDom.innerHTML = 0;
    this.domObj.appendChild(this.scoreDom);
  };
  Map.prototype.moveBg = function(){
    let top1 = -1106;
    setInterval(()=>{
      top1++;
      if(top1>=-253){
        top1 = -1106;
      }
      this.moveBox.style.top = top1+"px";
    },50);
  }
  var instance;
  return {
    getInstance:function(width,height,background){
      if(instance==undefined){
        instance = new Map(width,height,background);
      }else{
        instance.width = width;
        instance.height = height;
        instance.background = background;
        instance.domObj.style.width=this.width+"px";
        instance.domObj.style.height=this.height+"px";
        instance.moveBox.children[0].src=this.background;
        instance.moveBox.children[1].src=this.background;
      }
      return instance;
    }
  }
})();
// 单例模式的总结
/*采用闭包原理和自调用原理，先进行自调用噶、返回闭包函数，让使用者调用，但只能创建一个实例对象，当要创建多个的时候 不会进行创建，最上面简单案例代码，如果要再次创建实例，会覆盖之前的数据，并且不会创建实例对象
为什么要采用闭包 防止使用者再次构造新对象 采用自调用之后 函数执行1次 在调用时 只需要使用return的函数就行 避免用户多次构造新对象*/