JQuery check if select fields have a certain value and add required attribute
<p>Ok so, I would like to add the attribute required to a 'please specify' text box if the value of a dropdown/select includes 'please specify'.</p>

<p>I can make this field validate a single value using the code below but can't seem to check for all options. Need it to check if ANY of the selected options have 'please specify' and if so, this then applies the required Attribute. I've tried a million different ways and tried using an array but couldn't figure it. Sure it's super easy but any help would be amazing. Big thanks in advance!</p>

<p>HTML:
My select field </p>

<pre><code>&lt;select name="billing_customer_info" id="billing_customer_info" class="select " data-placeholder="Please select an option" allow_null="0" nulllabel="Please select an option" presentation="select" display="" hasselected="false"&gt;
  &lt;option value="Internet search Please specify"&gt;Internet search Please specify&lt;/option&gt;
  &lt;option value="Friend told me"&gt;Friend told me&lt;/option&gt;&lt;option value="Advertisement Please specify"&gt;Advertisement Please specify&lt;/option&gt;
  &lt;option value="Sticker"&gt;Sticker&lt;/option&gt;
  &lt;option value="Newspaper or magazine Please specify"&gt;Newspaper or magazine Please specify&lt;/option&gt;
  &lt;option value="Social media Please specify"&gt;Social media Please specify&lt;/option&gt;
  &lt;option value="Festival or show Please specify"&gt;Festival or show Please specify&lt;/option&gt;
  &lt;option value="In a shop"&gt;In a shop&lt;/option&gt;
&lt;/select&gt;
</code></pre>

<p>My field that needs to have the attribute added if select has please specify</p>

<pre><code>&lt;input type="text" class="input-text " name="billing_please_specify_here" id="billing_please_specify_here" placeholder="enter more information" display="text"&gt;
</code></pre>

<p>Jquery:</p>

<pre><code>$('select[name=billing_customer_info]').change(function () {
    if ($('select[name=billing_customer_info]').val() == 'Internet search Please specify'){
        $('input[name=billing_please_specify_here]').attr("required", true);
    } else {
        alert ('I dont need to be mandatory');
        $('input[name=billing_please_specify_here]').attr("required", false);
    }    
});
</code></pre>