* {

margin:0;

padding:0;

}

.class {

background:#000;

margin:10px;

height:50px;

}

<div id="test">

<div class="class">

</div>

<div class="class">

</div>

<div class="class">

</div>

<div class="class">

</div>

<div class="class">

</div>

</div>

var i;

var test = document.getElementById('test');

var testC = test.getElementsByTagName('div')

for(i=0;i<testC.length;i++) {

testC[i].onclick = function() {

for(i=0;i<testC.length;i++) {

if(testC[i] === this)

{

alert(i);

}

}

}

}