title: how to Disable multiple selected dropdown values in javascript
body: <p>I have one add button if i click it then it generates one new line having one dropdown(Multiple selection allowed) ,now if i ve selected some value in the dropdown next time if i press add button again it will generate
  the same dropdown in a new line but i want user should not able to select the previously selected items in the newly created dropdown.i.e each and every dropdown should have unique values selected.</p>
  
  <pre><code>&lt;select multiple="true" id="mySelect[0]"&gt;
    &lt;option value="1" &gt;Apple&lt;/option&gt;
    &lt;option value="2"&gt;Pear&lt;/option&gt;
    &lt;option value="3"&gt;Banana&lt;/option&gt;
    &lt;option value="4"&gt;Orange&lt;/option&gt;
  &lt;/select&gt;
  &lt;select multiple="true" id="mySelect[1]"&gt;
    &lt;option value="1" &gt;Apple&lt;/option&gt;
    &lt;option value="2"&gt;Pear&lt;/option&gt;
    &lt;option value="3"&gt;Banana&lt;/option&gt;
    &lt;option value="4"&gt;Orange&lt;/option&gt;
  &lt;/select&gt;
  &lt;select multiple="true" id="mySelect[2]"&gt;
    &lt;option value="1" &gt;Apple&lt;/option&gt;
    &lt;option value="2"&gt;Pear&lt;/option&gt;
    &lt;option value="3"&gt;Banana&lt;/option&gt;
    &lt;option value="4"&gt;Orange&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>if apple,pear is seleted in the 1st drop down then in next two dropdown apple option should be disabled and colored with red.</p>