Wordpress custom plugin widget jQuery val function not updating DOM

Wordpress custom plugin widget jQuery val function not updating DOM

I've got below code:
<form action="" method="post">
<div class="widget-content">
<p>
Youtube video will be displayed in this area. Please ensure
you input Youtube ID. Default width and height will be applied
if no values are provided on these fields.
</p>
<p>
<label for="widget-commstrat-youtube-2-title">Title:</label>
<input id="widget-commstrat-youtube-2-title"
name="widget-commstrat-youtube[2][title]" value=""
style="width:90%;">
</p>
<p>
<label for="widget-commstrat-youtube-2-youtube_id">Youtube
ID:</label>
<input id="widget-commstrat-youtube-2-youtube_id"
name="widget-commstrat-youtube[2][youtube_id]" value=""
style="width:90%;">
</p>
<p>
<label for="widget-commstrat-youtube-2-width">Width:</label>
<input id="widget-commstrat-youtube-2-width"
name="widget-commstrat-youtube[2][width]" value=""
style="width:90%;">
</p>
<p>
<label for="widget-commstrat-youtube-2-height">Height:</label>
<input id="widget-commstrat-youtube-2-height"
name="widget-commstrat-youtube[2][height]" value=""
style="width:90%;">
</p>
<p>
<input id="upload_image" type="text" size="36"
name="widget-commstrat-youtube[2][image_url]" value="http://">
<input id="upload_image_button" class="button" type="button"
value="Upload Image">
<br>Enter a URL or upload an image
</p>
</div>
<input type="hidden" name="widget-id" class="widget-id"
value="commstrat-youtube-2">
<input type="hidden" name="id_base" class="id_base"
value="commstrat-youtube">
<input type="hidden" name="widget-width" class="widget-width"
value="200">
<input type="hidden" name="widget-height" class="widget-height"
value="350">
<input type="hidden" name="widget_number" class="widget_number"
value="2">
<input type="hidden" name="multi_number" class="multi_number" value="">
<input type="hidden" name="add_new" class="add_new" value="">
<div class="widget-control-actions">
<div class="alignleft">
<a class="widget-control-remove" href="#remove">Delete</a> |
<a class="widget-control-close" href="#close">Close</a>
</div>
<div class="alignright">
<input type="submit" name="savewidget"
id="widget-commstrat-youtube-2-savewidget" class="button
button-primary widget-control-save right" value="Save">
<span class="spinner"></span>
</div>
<br class="clear">
</div>
</form>
I use jQuery('#upload_image').val('test'); to update but DOM is never
getting updated. This means I cannot see the change in the clientside on
my browser. All other fields get updated with same method without any
issues.
What could be wrong with this?