ajax传值到textbox的小问题

JScript code

function ajxstatechange(id) {       if (http_request.readyState == 4) {              if (http_request.status == 200) {                   //alert(http_request.responseText);                   document.getElementById(id).innerHTML=unescape(http_request.responseText);              } else {                   //document.write(http_request.responseText);                   alert('URL error'+http_request.responseText);              }       }}

<span id="id"></span>
如果是传到<input name="a" type="hidden" id="a">怎么做，指点一下

[解决办法]
document.getElementById('a').value = unescape(http_request.responseText);