How to make onclick event to work only once
<p>what I want to do is when someone click anywhere in the page.
A new window will open, but I want this to happen only once, so when someone click again on body, the function should not run.
Any advice? No jquery please.</p>
<pre><code>&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;body onclick=&quot;myFunction()&quot;&gt;
&lt;script&gt;
    function myFunction() {
        window.open(&quot;http://www.w3schools.com&quot;);
    }
&lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>