function getElementsByClassName(class,tag) 
  { 
  	var donus = new Array(); 
  	 
  	if ( tag == "" ) { 
  		tag = document.all; 
  	} else { 
  	} 
  	 
  	 
  	var x = document.getElementsByTagName(tag); 
  	for (var i=0;i<x.length;i++) { 
  		if ( x[i].className == class ) { 
  			donus.push(x[i]); 
  		} 
  	} 
  	return(donus); 
  }

<div class="as">as1</div> 
  <div class="as">as2</div> 
  <div class="es" id="myAnchor">es</div> 
  <span class="as">sapan</span> 
  <hr /> 
  <script> 
  var x; 
  x = getElementsByClassName('as','div'); 
  document.writeln(x[0].innerHTML); 
  </script>