<script>
function aa(str){
if(str=="1111"){
document.getElementById("span1").innerHTML="<b>弱</b>";
}else{
document.getElementById("span1").innerHTML="<b>强</b>";
}
}
</script>
<html><body>
<input type="password" name="pwd" value="" onchange="aa(this.value)"><span id=span1></span>
</body>
</html>