how to get child node by tag name
<p>I am trying to access child nodes. so far so good. my code is</p>

<p><code>columns = document.getElementById('columns').children[0].children;</code></p>

<p>where i and j are loops values.</p>

<p><code>collapseState = columns[i].children[j].children[2].style.display;</code></p>

<p>But i am try to get the element by tag name. Lets write:</p>

<p><code>collapseState = columns[i].children[j].children.getElementsByTagName('blahblah');</code></p>

<p>but it gives error. How to achieve this ?</p>