click event does not work with popupModal

[new2JS]

I am writing an add-on to parse/control one of the web-page that I am visiting regularly. Here is the snippet of code from the web-site:

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<div aria-labelledby="ui-dialog-title-popupModal" role="dialog" tabindex="-1" class="ui-dialog ui-widget ui-widget-content ui-corner-all ui-draggable ui-resizable" style="display: block; z-index: 1002; outline: 0px none; position: absolute; height: auto; width: 200px; top: 124px; left: 127px;">
<div class="ui-dialog-titlebar ui-widget-header ui-corner-all ui-helper-clearfix">
<span id="ui-dialog-title-popupModal" class="ui-dialog- title">
User Message
</span>
<a role="button" class="ui-dialog-titlebar-close ui-corner-all" href="#">
<span class="ui-icon ui-icon-closethick">
close
</span>
</a>
</div>

<div class="ui-dialog-content ui-widget-content" id="popupModal" style="width: auto; min-height: 72.1px; height: auto;">
<strong>
Your Message is Successfully Accepted
</strong>
<br>
<br>
<div style="float: right; margin-top: 10px;">
<input value="Close" onclick='$("#popupModal").dialog( "close" );' type="button">
</div>
</div>
</div>
-------------


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I am trying to write a add-on that will automatically click on the Button element said above. Here is my JS code in the add-on:

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var tabDoc = window.opener.gBrowser.getBrowserAtIndex(0).contentDocument;
var pop_ok = tabDoc.getElementById("popupModal").getElementsByTagName('input')[0];
if (pop_ok) {
var clkevt = tabDoc.createEvent("MouseEvents");
clkevt.initEvent("dblclick",true,true);
pop_ok.dispatchEvent(clkevt);
}
-------------

But it does not close the popupModal alert automatically. I could see that it finds an button object and goes inside "if (pop_ok)" condition. But it does not trigger the button event. I tried both "click" and "dblclick", but without success.

Can I get some help here to understand what's going on and why click event does not close the popupModal alert?
I am new to JS, so please....please.... help.

Thanks in advance.

 

[new2JS]

Can anyone help me to resolve above issue???