vue通过url方式展示PDF的几种方法

        npm i pdfjs-dist@2.5.207 --save
        npm i vue-pdf@4.2.0 --save

        "dependencies": {
                  "pdfjs-dist": "2.5.207",
                  "vue-pdf": "4.2.0",
          }

fileLinkToStreamDownload(url) {
      let fileName = this.getDay()
      let reg = /^([hH][tT]{2}[pP]:\/\/|[hH][tT]{2}[pP][sS]:\/\/)(([A-Za-z0-9-~]+).)+([A-Za-z0-9-~\/])+$/
      if (!reg.test(url)) {
        throw new Error('传入参数不合法,不是标准的文件链接')
      } else {
        let xhr = new XMLHttpRequest()
        xhr.open('get', url, true)
        xhr.setRequestHeader('Content-Type', `application/pdf;charset-UTF-8`)
        xhr.responseType = 'blob'
        let that =this
        xhr.onload = function() {
          if (this.status == 200) {
            //接受二进制文件流
            var blob = this.response
            // that.downloadExportFile(blob, fileName);
            that.blobToBase64(blob).then(res => {
                // blob转base64
                let baseArr = res.split(',');
                that.showPdf(baseArr[1]);
              })
          }
        }
        xhr.send()
      }
    },
     //Blob类型转BASE64
      blobToBase64(blob) {
      return new Promise((resolve, reject) => {
        const fileReader = new FileReader();
        fileReader.onload = (e) => {
          resolve(e.target.result);
        };
        // readAsDataURL
        fileReader.readAsDataURL(blob);
        fileReader.onerror = () => {
          reject(new Error('blobToBase64 error'));
        };
      });
    },
    getDay() {
      let time = new Date(),
      year = time.getFullYear(),
      month = time.getMonth() + 1,
      day = time.getDate(),
      timeStem = time.getTime()
      return `${year}/${month}/${day}/${timeStem}.pdf`
    },

async showPdf(base64Val) {
      let pdfList = document.querySelector('.pdfList') //通过querySelector选择DOM节点,使用document.getElementById()也一样
      let base64 = base64Val //获得bas464编码
      let decodedBase64 = window.atob(base64) //使用浏览器自带的方法解码
      let pdfCurrent = await PDFJS.getDocument({data: decodedBase64}) //返回一个pdf对象
      let pages = pdfCurrent.numPages //声明一个pages变量等于当前pdf文件的页数
      for (let i = 1; i <= pages; i++) { //循环页数
        let canvas = document.createElement('canvas') 
        let page = await pdfCurrent.getPage(i) //调用getPage方法传入当前循环的页数,返回一个page对象
        let scale = 1;//缩放倍数，1表示原始大小
        let viewport = page.getViewport(scale); 
        let context = canvas.getContext('2d'); //创建绘制canvas的对象
        canvas.height = viewport.height; //定义canvas高和宽
        canvas.width = viewport.width;
        let renderContext = {
          canvasContext: context,
          viewport: viewport
        };
        await page.render(renderContext)
        canvas.className = 'canvas' //给canvas节点定义一个class名,这里我取名为canvas
        pdfList.appendChild(canvas) //插入到pdfList节点的最后
      }
    },