求改错

<script>
function time(){
var b=new Date();
var str="北京时间：";
var oTxt1=document.getElementById("t1");
var hour;
var minu;
var sec;
if(b.getHours()<10)
{
hour="0"+b.getHours();
}
if(b.getMinutes()<10)
{
minu="0"+b.getMinutes();
}
if(b.getSeconds()<10)
{
sec="0"+b.getSeconds();
}
var str=str+hour+"："+minu+"："+sec;
oTxt1.value=str;
setTimeout("time()",1000)
}
time();
</script>
第二次写还是不对

<script>
function time(){
var b=new Date();
var str="北京时间：";
var oTxt1=document.getElementById("t1");
var hour;
var minu;
var sec;
if(b.getHours()<10)
{
hour="0"+b.getHours();
}
if(b.getMinutes()<10)
{
minu="0"+b.getMinutes();
}
if(b.getSeconds()<10)
{
sec="0"+b.getSeconds();
}
var str=str+"hour"+"："+"minu+""："+"sec";
oTxt1.value=str;
setTimeout("time()",1000)
}
time();
</script>
第三次