html文件上传保存-（.html and string translate into .html ）

//上传h5编辑器编辑的html内容
    uploadHtml(newsId?: any) {
     const news = newsId !== undefined ? newsId : 'new';
     let uploadFile = this.dataURLtoBlob(`data:text/html;base64,${new Buffer(this.newsInfo.content).toString('base64')}`) ;
        let form = new FormData();
        form.append(`news_${news}.html`, uploadFile , `news_${news}.html`);
        return this.smartrecService.uploadFile(form, 'html');
    }

    //将h5编辑器编辑好的html内容组装成blob对象
    dataURLtoBlob(dataurl: string) {
        const arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],
          bstr = atob(arr[1]);
        let n = bstr.length;
        const u8arr = new Uint8Array(n);
        while (n--) {
          u8arr[n] = bstr.charCodeAt(n);
        }
        return new Blob([u8arr], { type: mime });
    }

 //通过contentId获取h5编辑器编辑的html内容,并转化为字符串
 getHtml(contentId: any): void {
  const url = this.smartrecService.getContentUrlById(contentId);
  let xhr = new XMLHttpRequest();
　　 xhr.open('GET', url);
  xhr.responseType = "arraybuffer";
  xhr.send();
  xhr.onreadystatechange = function() {
 　　　　if ( xhr.readyState == 4 && xhr.status == 200 ) {
       const htmlBuffer = new Buffer(new Uint8Array(xhr.response));
       const htmlStr = htmlBuffer.toString();
       try {
              JSON.parse(htmlStr);
          } catch(e) {
             this.newsInfo.content = htmlStr;
          }
 　　　　}
　　　　}.bind(this);
 }