file_upload.pt

<tal:block tal:define="oid oid|field.oid;
        css_class css_class|field.widget.css_class;
        style style|field.widget.style;
        preview_url cstruct.get('preview_url')|cstruct.get('base64')|'';
        ext str(cstruct.get('filename').split('.')[-1:][0]).lower()|[];
        fname str(cstruct.get('filename'))|'';
        delete cstruct.get('delete')|'';">
    ${field.start_mapping()}
    <img id="preview-${oid}" alt="" src="${preview_url}" style="width:100px;height:auto;display:block;"
        onload="window.URL.revokeObjectURL(this.src);"></img>
    <a id="label-${oid}" tal:condition="preview_url" class="label label-default" href="${preview_url}"
    target="_blank"><i class="fa fa-search"></i> View</a>
    <input type="file" name="upload" id="${oid}"
             tal:attributes="style style;
                    accept accept|field.widget.accept;
                    data-filename fname;
                    attributes|field.widget.attributes|{};"
                    onchange="document.getElementById('preview-'+this.id).src = window.URL.createObjectURL(this.files[0]);
                              document.getElementById('labeldelete-'+this.id).remove();
                              document.getElementById('label-'+this.id).remove();"/>
    <input tal:define="uid cstruct.get('uid')"
             tal:condition="uid"
            type="hidden" name="uid" value="${uid}"/>
        ${field.end_mapping()}
    <script type="text/javascript">
        deform.addCallback('${oid}', function (oid) {
            $('#' + oid).upload();
        });

    </script>
</tal:block>