背景：碰到了在当前页面预览pdf（不打开新的窗口，采用iframe），并下载。

一、pdf的预览

1.在适合位置嵌入iframe标签

  <iframe :src="pdfUrl" frameborder="0" width="100%" :style="{height: tableHeight,overflow:'auto'}"></iframe>

2.在methods中添加相应方法

pdfPreview(val) {
      this.previewDownFile(val).then(v => {
        if (v.status == 200) {
          const binaryData = [];
          binaryData.push(v.data);
          let url = window.URL.createObjectURL(new Blob(binaryData, {type: 'application/pdf'}));
          this.pdfUrl = url
        } else {
          this.$message.error("请求错误！");
        }
      })
    },


   previewDownFile(val) {
      return new Promise((resolve, reject) => {
        this.$axios({
          url: `file-server/download/annex/${val.value}`,
          timeout: 0,
          method: 'get',
          responseType: 'blob',
          header: {"Content-Type": "multipart/form-data"},
        }).then(res => {
          resolve(res)
        }).catch(() => {
          resolve(false);
        });
      });
    },

二、pdf的下载

    pdfUpdate() {
      this.previewDown().then(v => {
        if (v.status == 200) {
          if (!v) {
            return;
          } else {
            const elink = document.createElement("a");
            // console.log(new Blob([v.data]));
            elink.href = window.URL.createObjectURL(new Blob([v.data], {type: `application/pdf`}));
            elink.style.display = 'none';
            elink.setAttribute('download', this.tabData.dataCateName);
            document.body.appendChild(elink);
            elink.click();
            URL.revokeObjectURL(elink.href); // 释放URL 对象
            document.body.removeChild(elink);
          }
        }
      })
    },


 previewDown() {
      return new Promise((resolve, reject) => {
        this.$axios({
          url: `file-server/download/${this.emitData.fileId}`,
          timeout: 0,
          method: 'get',
          responseType: 'blob',
          header: {"Content-Type": "multipart/form-data"},
        }).then(res => {
          resolve(res)
        }).catch(() => {
          resolve(false);
        });
      });
    },

总结：其实但看代码还是蛮简单的。但是实际操作的时候，还是费了一番功夫。