1.       //下载图片
    2.       download() {
    3.         let imgData = 'data:image/png;base64,iVBORw0KGgoAAAANSUh........';
    4.         this.downloadFile('测试.png', imgData);
    5.       },
    6.       //下载
    7.       downloadFile(fileName, content) {
    8.         let aLink = document.createElement('a');
    9.         let blob = this.base64ToBlob(content); //new Blob([content]);
    11.         let evt = document.createEvent("HTMLEvents");
    12.         evt.initEvent("click", true, true);//initEvent 不加后两个参数在FF下会报错  事件类型，是否冒泡，是否阻止浏览器的默认行为
    13.         aLink.download = fileName;
    14.         aLink.href = URL.createObjectURL(blob);
    16.         // aLink.dispatchEvent(evt);
    17.         //aLink.click()
    18.         aLink.dispatchEvent(new MouseEvent('click', {bubbles: true, cancelable: true, view: window}));//兼容火狐
    19.       },
    20.       //base64转blob
    21.       base64ToBlob(code) {
    22.         let parts = code.split(';base64,');
    23.         let contentType = parts[0].split(':')[1];
    24.         let raw = window.atob(parts[1]);
    25.         let rawLength = raw.length;
    27.         let uInt8Array = new Uint8Array(rawLength);
    29.         for (let i = 0; i < rawLength; ++i) {
    30.           uInt8Array[i] = raw.charCodeAt(i);
    31.         }
    32.         return new Blob([uInt8Array], {type: contentType});
    33.       },