The problem is your jQuery selector in your JavaScript code. When Splunk renders the dashboard, the ID may not be associated with the input element depending on your Splunk version. For instance, here is a snippet of how your dashboard rendered on Splunk 7.1.2:
<div class="splunk-view splunk-textinput" id="URLs_only_10923" data-view="splunkjs/mvc/textinputview">
<div data-size="medium" data-test="text" data-test-value="" data-component="splunk-core:/splunkjs/mvc/components/TextInput" class="main_Box_c14abce54916ca6a_f7b2da main_Text_cd96be7d8632d6e1_f7b2da">
<input type="text" class="input_Text_cd96be7d8632d6e1_f7b2da" value="" aria-multiline="false" data-test="textbox" autocomplete="on" role="textbox" tabindex="0">
</div>
</div>
Notice the ID is on a <div> instead of an input. Also, notice that the ID was modified. The following modification to your JavaScript should help:
$("[id^=URLs_only]")
.find("input")
.on("change", function() {
This jQuery selector is looking for an ID that starts with URLs_only (which will be your <div> ). Then, it looks for the input element within that element and carries on.
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