//下載圖片
      download() {
        let imgData = 'data:image/png;base64,iVBORw0KGgoAAAANSUh........';
        this.downloadFile('測試.png', imgData);
      },
      //下載
      downloadFile(fileName, content) {
        let aLink = document.createElement('a');
        let blob = this.base64ToBlob(content); //new Blob([content]);

        let evt = document.createEvent("HTMLEvents");
        evt.initEvent("click", true, true);//initEvent 不加後兩個引數在FF下會報錯  事件型別，是否冒泡，是否阻止瀏覽器的預設行為
        aLink.download = fileName;
        aLink.href = URL.createObjectURL(blob);
        // aLink.dispatchEvent(evt);
       // aLink.click()
        aLink.dispatchEvent(new MouseEvent('click', {bubbles: true, cancelable: true, view: window}));//相容火狐
      },
      //base64轉blob
      base64ToBlob(code) {
        let parts = code.split(';base64,');
        let contentType = parts[0].split(':')[1];
        let raw = window.atob(parts[1]);
        let rawLength = raw.length;

        let uInt8Array = new Uint8Array(rawLength);

        for (let i = 0; i 
 
< rawLength; ++i) {
          uInt8Array[i] = raw.charCodeAt(i);
        }
        return new Blob([uInt8Array], {type: contentType});
      }