File upload with conditions and input text value

<!--here is the html-->
<input id="txt" type = "text" value = "Choose File" onclick ="javascript:document.getElementById('file').click();">
<input id = "file" class="upload-opt" type="file" style='display: none;' name="upload"/>


<!--here is the script-->
$('#file').on( 'change', function() {
           var myfile= $( this ).val();
           var ext = myfile.split('.').pop();
           //alert(ext);
           if(ext=="pdf" || ext=="docx" || ext=="doc" || ext=="txt" || ext=="odc" || ext=="jpg" ){
                    if(this.files[0].size > 1048576){
                       $('.upload-opt').next('.validation-text').text('File is too big!');
                       this.value = "";
                    } else {
                        var value = $(this).val();
                        $("#txt").val(value);
                    }
           } else {
                $('.upload-opt').next('.validation-text').text('This kind of file cant be uploaded');
                this.value = "";
           }
        });