代码如下：

const dataURL = canvas.toDataURL({format: "png",width: 400,height: 400,
});const link = document.createElement("a");
link.download = new Date().getTime();link.href = dataURL;
document.body.appendChild(link);
link.click();
document.body.removeChild(link);

结果虽然文件是下下来了，但是浏览器出现以下报错

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解决方法，改成

const dataURL = canvas.toDataURL({format: "png",width: 400,height: 400,
});const link = document.createElement("a");let blob = dataURLtoBlob(dataURL);
let url = URL.createObjectURL(blob);link.download = new Date().getTime();link.href = url;
document.body.appendChild(link);
link.click();
document.body.removeChild(link);// 将Base64字符串转换为Blob对象
function dataURLtoBlob(dataurl) {var arr = dataurl.split(',');var mime = arr[0].match(/:(.*?);/)[1];var bstr = atob(arr[1]);var n = bstr.length;var u8arr = new Uint8Array(n);while(n--) {u8arr[n] = bstr.charCodeAt(n);}return new Blob([u8arr], {type:mime});
}

简言之，就是把
link.href = dataURL;改成
let blob = dataURLtoBlob(dataURL);
let url = URL.createObjectURL(blob);
link.href = url;