前端实现预加载

/*
 * @Description: 预加载
 * @Author: wangrui
 * @Date: 2021-03-02 13:35:34
 */
class PreLoad{
  constructor(){
    this.images=[]
    this.opts={
      success:null,
      fail:null
    }
  }
  preLoadFn(images,opts){
    this.images=typeof(images)==='string'?[images]:images;
    this.opts={...this.opts,...opts};
    let count=0;

    for(var i=0;i<this.images.length;i++){
      if(typeof(this.images[i])!=='string')return;
      const imageFn=new Image();
      imageFn.setAttribute('crossOrigin', 'anonymous');
      imageFn.onload=()=>{
        this.commonFn(count);
        count++;
      }
      imageFn.onerror=()=>{
        this.commonFn(count);
        count++;
      }
     
      imageFn.src=this.images[i];
    }
  }

  commonFn(count){
    this.opts.fail&&this.opts.fail()
    if(this.images.length-1===count){
      this.opts.success&&this.opts.success()
    }
  }
}
export default new PreLoad();