JSFiddle - React, Tailwind, and code Playground
by mowglisanu
HTML
<select multiple="multiple" name="addtextarea" id="studentadd" size="10">
<option value='1'>u08743 - Joe Cann</option>
<option selected value='4'>u03043 - Jill Sanderson</option>
<option selected value='7'>u08343 - Craig Moon</option>
</select>
<select id="studentselect" name="studenttextarea">
<option value='1'>u08743 - Joe Cann</option>
<option value='4'>u03043 - Jill Sanderson</option>
<option value='7'>u08343 - Craig Moon</option>
</select>
JavaScript
var selectedOption = $('#studentadd').find(':selected');
var studentSelect = $('#studentselect');
selectedOption.each(function(){
studentSelect.find('[value="'+this.value+'"]').remove();
});