前端请求设置 responseType: “blob”

后台接口返回的文件流如下：

拿到后端返回的文件流后：
预览

<iframe  :src="previewUrl" frameborder="0" style="width: 500px; height: 500px;"></iframe>

1、预览

view(data) {
     // 文件类型            
     let fileType = this.fileName.slice(this.fileName.length - 3).toUpperCase();
     let myBlob = '';
     //不同文件类型设置不同的type            
     if (fileType == 'PDF') {
          myBlob = new window.Blob([data], { type: 'application/pdf' });
     } else {
          myBlob = new window.Blob([data], { type: 'image/png' });
     }
     const previewUrl = window.URL.createObjectURL(myBlob);
     this.previewUrl = previewUrl;// iframe预览
    // window.open(previewUrl, '_blank');// 浏览器新打开窗口        
},

2、下载

// 下载        
downFile() {
   var data = this.fileData;
   var fileType = this.fileName.slice(this.fileName.length - 3).toUpperCase();
   var blob = "";
   if (fileType == 'PDF') {
       blob = new window.Blob([data], { type: 'application/pdf' });
   } else if (fileType == 'PNG') {
       blob = new window.Blob([data], { type: 'image/png' });
   }
   const a = document.createElement("a");
   const objectUrl = URL.createObjectURL(blob);
   a.setAttribute("href", objectUrl);
   a.setAttribute("download", this.fileName);
   a.click();
   URL.revokeObjectURL(a.href); // 释放url        
}