[jahman]

<div><input class = "input" value = "1"></div>
<div><input class = "input" value = "2"></div>
<div><input class = "input" value = "3"></div>

<script>
var arr = document.getElementsByClassName('input'),
len = arr.length,
data = [];

for (var i=0; i < len; i++){

  data.push(arr[i].value);
  
}

alert("Inputs: "+len+'\n'+data);
</script>

вот тут сравнение есть наглядное
http://jsperf.com/getelementsbyclass...selectorall/18