总结:先用变量获取对象,然后对变量进行if()else的判断,得到结果
<!DOCTYPE html>
<html>
<head>
<title>微博输入</title>
<style type="text/css">
body{font-size:12px; }
.box{width: 600px;height: 160px;border: 10px solid pink; margin: 0px auto;padding: 10px;}
#bg{float: left;height: 25px;}
.box1{float: left;margin-left: 255px;width: 150px;height: 25px;text-align: right;font-size: 14px;color: #888;}
.box1 span{font-size: 16px;font-weight: bold;}
#text{width: 600px;height: 100px;border: 1px solid #888;margin-top: 5px;}
.box #sp1,#sp2,#sp3,#sp4,#sp5,#sp6{float: left;width: 30px;height: 32px;line-height: 32px;padding-left: 32px;}
#sp6{margin-left: 120px;margin-right: 10px;color: #888;}
#bt{float: left;width: 80px;height: 30px;border: none;background:#ffc09f;color:#fff; border-radius: 5px;}
</style>
<script type="text/javascript">
var text,number,m
window.onload=function(){
text=document.getElementById('text')
number=document.getElementById('number')
bt=document.getElementById('bt')
text.onkeyup=function aa(){
m=140-text.value.length
if(m<0){
number.style.color="red"
}else{
number.style.color="#888"
}
number.innerHTML=m
}
bt.onclick=function(){
if(m==140){
alert("你还没有输入!")
text.focus()
}else if(m<0){
alert("你输入 的字数过多,不可以发布!!!")
text.focus()
}else{
alert("发布成功!!!")
}
}
aa()
}
</script>
</head>
<body>
<div class="box">
<span id="bg">有什么新鲜事???</span>
<div class="box1">还可以输入<span id="number"></span>字</div>
<textarea id="text" ></textarea>
<span id='sp1'>表情</span>
<span id='sp2'>图片</span>
<span id='sp3'>视频</span>
<span id='sp4'>话题</span>
<span id='sp5' style="width: 40px;">长微博</span>
<span id='sp6'>公开</span>
<input type="button" name="" value="发布" id="bt">
</div>
</body>
</html>