JS截取base64图片格式上传，最佳的方式是split而不是replace

    var image = "data:image/jpg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRofHh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL";
    var str = image.split(',')[1];
    console.log(str)