It seems that there is no event for resizing a textarea.
You could check out the following answer on an older question:
https://stackoverflow.com/a/7055239/1537154
You can modify this to update al other textareas:
http://jsfiddle.net/tsx1yxj3/
jQuery(document).ready(function(){
var $textareas = jQuery('textarea');
// store init (default) state
$textareas.data('x', $textareas.outerWidth());
$textareas.data('y', $textareas.outerHeight());
$textareas.mouseup(function(){
var $this = jQuery(this);
if ( $this.outerWidth() != $this.data('x')
|| $this.outerHeight() != $this.data('y') )
{
// Resize Action Here
$('textarea').height($this.outerHeight());
$('textarea').width($this.outerWidth());
}
// store new height/width
$this.data('x', $this.outerWidth());
$this.data('y', $this.outerHeight());
});
});
Resizing only kicks in after your done and there are some other limitations.
You could also look at a jquery UI implementation:
http://jqueryui.com/resizable/