JavaScript - Simular click de un objeto sin id

<script type="text/javascript">

var obj = document.getElementById("godetein");

if (obj){

   obj.click();

}

</script>

<li class="filter" data-filter="portfolio_category_138"><span>Alicante</span></li>

<li class="filter" data-filter="portfolio_category_139"><span>Cádiz</span></li>

var obj = findByAttrValue('li', 'data-filter', 'portfolio_category_138');

 if (obj) {

 obj.click();

 }

 function findByAttrValue(tag, attr, value) {

 var obj = null;

 var allObjects = document.getElementsByTagName(tag);

 for (var i = 0; i < allObjects .length && obj == null; i++) {

 if (allObjects[i].getAttribute(attr) == value) {

 obj = allObjects[i];

 }

 }

 return obj ;

 }

var obj = document.getElementsByClassName('filter');

if (obj[0]) {

    obj[0].click();

}