Catch upload errors

<!--element -->
<textarea id="content"></textarea>

<!-- call -->
<script>
$R('#content', {
    imageUpload: '/your-image-upload-script/',
    fileUpload: '/your-file-upload-script/',
    callbacks: {
        image: {
            uploadError: function(response)
            {
                console.log(response.message);
            }
        },
        file: {
            uploadError: function(response)
            {
                console.log(response.message);
            }
        }
    }
});
</script>

<!-- server response json -->
{
    "error": true,
    "message": "Something went wrong..."
}