我自己写的案例
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<!-- <link rel="stylesheet" href="./css/index.css"> -->
<title>Document</title>
<style type="text/css">
body{font-size: 12px;}
.box{width: 600px;height: 160px;border:10px solid pink; margin: 0px auto;padding:10px; }
img{float: left;}
.box1{float: left;margin-left: 255px;width: 150px;height: 24px;text-align: right;font-size: 14px;color: #888;}
.box1 span{font-size: 16px;font-weight: bold;}
#text{width:600px;height: 100px;border: 1px solid #ccc;margin-top: 5px;}
.box #sp1,#sp2,#sp3,#sp4,#sp5,#sp6{float: left;width: 30px;height: 32px;line-height: 32px;padding-left: 26px;}
#sp1{background: url(images/an5.png) no-repeat left center;}
#sp2{background: url(images/an4.png) no-repeat left center;}
#sp3{background: url(images/an3.png) no-repeat left center;}
#sp4{background: url(images/an2.png) no-repeat left center;}
#sp5{background: url(images/an1.png) no-repeat left center;width: 40px;}
#sp6{ margin-left: 158px;margin-right:15px;color: #888; }
#bt{float: left;width: 80px;height: 30px;border: none;background: #ffc09f;color: #fff;border-radius: 5px;}
</style>
<script type="text/javascript">
let 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("字数太多，不可以发布")
text.focus()
}else{
alert("发布成功")
}
}
aa()
}
</script>
</head>
<body>
<div>
<img src="images/12.png">
<div>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">长微博</span>
<span id="sp6">公开</span>
<input type="button" value="发布" id="bt">
</div>
</body>
</html>