创建 a 标签下载文件/图片

// 附件下载
const downLoadImg = (imgsrc, name) => {
    var image = new Image();
    // 解决跨域 Canvas 污染问题
    image.setAttribute("crossOrigin", "anonymous");
    image.onload = function() {
      var canvas = document.createElement("canvas");
      canvas.width = image.width;
      canvas.height = image.height;
      var context = canvas.getContext("2d");
      context.drawImage(image, 0, 0, image.width, image.height);
      var url = canvas.toDataURL("image/png"); //得到图片的base64编码数据

      var a = document.createElement("a"); // 生成一个a元素
      var event = new MouseEvent("click"); // 创建一个单击事件
      a.download = name || "photo"; // 设置图片名称
      a.href = url; // 将生成的URL设置为a.href属性
      a.dispatchEvent(event); // 触发a的单击事件
    };
    image.src = imgsrc;
}