Values Get Removed After Adding Another Field

I type something on the current textarea/input and all the values get removed after I add another field.

<script language="Javascript" type="text/javascript">
<!--
//Add more fields dynamically.
function addField(area,field,limit) {
if(!document.getElementById) return; //Prevent older browsers from getting any further.
var field_area = document.getElementById(area);
var all_inputs = field_area.getElementsByTagName("input"); //Get all the input fields in the given area.
//Find the count of the last element of the list. It will be in the format '<field><number>'.

If the
//field given in the argument is 'friend_' the last id will be 'friend_4'.
var last_item = all_inputs.length - 1;
var last = all_inputs[last_item].id;
var count = Number(last.split("_")[1]) + 1;

//If the maximum number of elements have been reached, exit the function.
//If the given limit is lower than 0, infinite number of fields can be created.
if(count > limit && limit > 0) return;
//Older Method
field_area.innerHTML += "<li><textarea id='steps' name='steps[]' rows='5' cols='40'>