预加载

function preLoad(options){
  this.options=options;
  var defaluts={
      imgArr:[],
      video:[]
  }
  if(!options){
      for(var i in defaluts){
          this.options[i]=defaluts[i]
      }
  }
}
preLoad.prototype.upLoad=function(){
    var tmp =0,_this=this;
    for(var i=0;i<this.options.imgArr.length;i++){

        var image= new Image();
        image.src=this.options.imgArr[i];
        image.onload=function () {
            tmp++;
            if(tmp==_this.options.imgArr.length-1){
                _this.End();
            }
        }
    }
}
preLoad.prototype.End=function () {
    console.log("加载结束")
    //fn1()
}
var loadder=new preLoad({
    imgArr:[
      "../img/1.jpg",
      "../img/1.jpg"
    ]
})
loadder.upLoad();