Count elements with class name with javascript
<script>
var docElems = document.getElementsByClassName('doc');
for(var i = 0; i < docElems.length; i++) {
docElems[i].style.minHeight = '100px';
}
</script>
<div class="container">
<div class="doc"></div>
<div class="doc"></div>
<div class="doc"></div>
<div class="doc"></div>
<div class="doc"></div>
</div>