a标签下载文件，图片，txt文件

使用a标签下载文件的时候设置下载文件的文件名

给a标签加一个download属性    可以设置下载下来的文件的文件名    

注意：下载的地址域名和访问网站的域名是同源  否则设置无效

    // 下载图片
    downloadIamge(swiperItem) {//下载图片地址和图片名
      console.log('swiperItem', swiperItem)
      // let src = 'http://pic.c-ctrip.com/VacationH5Pic/mice/wechat/ewm01.png';
      let src = 'https://rds.wm-motor.cn/file-proxy/?url=' + encodeURI(swiperItem.path)
        var canvas = document.createElement('canvas');
        var img = document.createElement('img');
        img.onload = function(e) {
            canvas.width = img.width;
            canvas.height = img.height;
            var context = canvas.getContext('2d');
            context.drawImage(img, 0, 0, img.width, img.height);
            canvas.getContext('2d').drawImage(img, 0, 0, img.width, img.height);
            canvas.toBlob((blob)=>{
                let link = document.createElement('a');
                link.href = window.URL.createObjectURL(blob);
                link.download = swiperItem.docName; 
                link.click();  
            }, "image/jpeg");
        }
        img.setAttribute("crossOrigin",'Anonymous');
        img.src = src;
    },

  ,

　　

 // 下载文件，区分txt文件
    handleDownload(swiperItem){
　　　　// txt文件
      if(swiperItem.docName.split(".")[1] == 'txt'){
        this.urlToBlob(swiperItem).then(() => {
          let url = new Blob(['ufeff' + this.txtContent], {type: 'text/tet,charset=UTF-8'});
          swiperItem.path = URL.createObjectURL(url);
          const a = document.createElement('a')
          a.setAttribute('download', swiperItem.docName)
          a.setAttribute('target', '_blank')
          a.setAttribute('href', swiperItem.path)
          a.click()
        })
        // openDownloadDialog(blob, `${fileName}.csv`);
      }else {
　　　　//其他文件
        const a = document.createElement('a')
        
        a.setAttribute('target', '_blank')
        let path = 'https://rds.wm-motor.cn/file-proxy/?url=' +  encodeURI(swiperItem.path)
        a.setAttribute('href', path)
        a.setAttribute('download', swiperItem.docName)
        a.click()
      }
      
    }