Question

How to count the total number of div elements that are contained in another div using javascript?

Answer 1

The getElementsByTagName() is not only a document method, but one that can run on any DOM element.

element.getElementsByTagName is
similar to
document.getElementsByTagName, except
that its search is restricted to those
elements which are descendants of the
specified element

see more at https://developer.mozilla.org/en/DOM/element.getElementsByTagName

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So the actual code that does what you ask is

var container_div = document.getElementById('id_of_container_div');
var count = container_div.getElementsByTagName('div').length;