abstract：<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>輸入字?jǐn)?shù)</title> <style> *{margin: 0;padding: 0;} textarea{
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>輸入字?jǐn)?shù)</title>
<style>
*{margin: 0;padding: 0;}
textarea{margin: 100px auto 0;display: block;background: #aefffe;}
button{width: 80px;height: 30px;background:blue;border-radius: 3px;color:white;margin: 20px auto 0;display: block;}
button:hover{cursor: pointer;}
div div{width: 400px;margin:20px auto;}
</style>
</head>
<body>
<div id="txt">
<textarea id="txtInput" cols="100" rows="10" onkeyup="txtChange()" placeholder="請輸入文字"></textarea><br>
<div><span>您已輸入</span><span id="txtCount">0</span><span>個字符，還可以輸入</span><span id="txtLeft">140</span><span>個字符</span></div>
<button id="mysubmit" type="button" onclick="mysubmit()">提交</button>
</div>
</body>
<script>
var txtCount = document.getElementById("txtCount");
var txtInput = document.getElementById("txtInput");
var txtLeft = document.getElementById("txtLeft");
function txtChange(){
txtCount.innerText=txtInput.value.length;
txtLeft.innerText = 140-txtInput.value.length;
}
function mysubmit(){
if(txtLeft.innerText==140){
alert("輸入不能為空");
}else if(txtLeft.innerText<0){
alert("不能超過140字");
}else{alert("提交成功")};
}
</script>
</html>
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效果圖
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思路：
1、兩個span用于實(shí)時(shí)計(jì)數(shù)
2、js獲取文本域的值的長度
3、onkeyup事件觸發(fā)給span文本賦值上一步獲取的文本長度
4、點(diǎn)擊提交按鈕時(shí)，對字?jǐn)?shù)進(jìn)行判斷，字?jǐn)?shù)為零或字?jǐn)?shù)超過140時(shí)，彈出警告信息
Correcting teacher：天蓬老師Correction time：2019-04-13 21:55:24
Teacher's summary：你的變量與函數(shù)的命名非常的規(guī)范, 事件也運(yùn)行的正確...
順便說一下,微博早已取消字?jǐn)?shù)限制了