鼠标滑过显示文字，动态显示文本框中的字数

<script>
//定义文本框当前长度
var slength = document.getElementById('textarea').value.replace(/\s/gi, "").length;

//定义文本框最大长度
var maxLength=500;

var initStr="\n欢迎使用派能在线语音合成系统。\n"
                 +"请先在此输入文字，然后按［阅读］按钮及聆听结果。\n"
                 +"如有任何查询或意见，请电邮到[e-mail]\n"; 

document.getElementById('textarea').innerHTML=initStr;
validateText();

//mouseover
function onTipsShowing(svalue){	
      document.getElementById('tips').innerHTML=svalue;
}

//mouseout
function onTipsRestoring(){	
if(maxLength<slength){
		document.getElementById('tips').innerHTML='<font color=red>'+slength+'</font>个字(字数上限:'+maxLength+')';
	}
	else{
		document.getElementById('tips').innerHTML=slength+'个字(字数上限:'+maxLength+')';
	}
}


function validateText(){
	 slength = document.getElementById('textarea').value.replace(/\s/gi, "").length;
}
	
</script> 




<div style="float: left">
<select id="speakingRate"
	onmouseover="document.getElementById('tips').innerHTML= '改变合成语速'"
	onmouseout=" onTipsRestoring()">
	<option value="100">慢</option>
	<option value="90" selected="selected">普通</option>
	<option value="80">快</option>
</select>

<button id="synthesize" type="button "
	onmouseover="onTipsShowing('请阅读下面的文字')" 
       onmouseout="'">朗读</button>

<button id="reset" type="button"
	onmouseover="onTipsShowing('将下面的文本重设为初始文本')"
	onmouseout="onTipsRestoring()"
	onmousedown="document.getElementById('textarea').innerHTML=initStr;validateText();">
重设</button>

<button id="clear" type="button"
	onmousemove="onTipsShowing('清除下面文本的内容')" 
       onmouseout="onTipsRestoring()"
	onmousedown="document.getElementById('textarea').innerHTML=''">清除</button>

</div>