Javascript create element ทำการ autocomplete ยังไงครับ

<script language="javascript">

	function fncCreateElement(){
	   var mySpan = document.getElementById('mySpan');
	   var myLine = document.getElementById('hdnLine');
	   myLine.value++;
  
// Create input text treat_amount
	  var myElement1 = document.createElement('input');
	  myElement1.setAttribute('type',"text");
	  myElement1.setAttribute('name',"open_amount"+myLine.value);
	  myElement1.setAttribute('id',"open_amount"+myLine.value);
	  myElement1.setAttribute('class',"form-control");
	  myElement1.setAttribute('placeholder',"Serail No.");
	  //myElement1.setAttribute('style',"width:30%");
	  mySpan.appendChild(myElement1);	
		
       // Create <br>
	   var myElement4 = document.createElement('br');
	   myElement4.setAttribute('name',"br"+myLine.value);
	   myElement4.setAttribute('id',"br"+myLine.value);
	   mySpan.appendChild(myElement4);

	}

	function fncDeleteElement(){
		var mySpan = document.getElementById('mySpan');
		var myLine = document.getElementById('hdnLine');
		if(myLine.value >= 0)
		{
			// Remove input text
			var deleteFile = document.getElementById("open_amount"+myLine.value);
			mySpan.removeChild(deleteFile);
			// Remove <br>
			var deleteBr = document.getElementById("br"+myLine.value);
			mySpan.removeChild(deleteBr);
			myLine.value--;
		}
	}
</script>