<!DOCTYPE html>
<html lang="en">
<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">
<title>Document</title>
<style>
* {
margin: 0;
padding: 0;
}
.search {
position: relative;
width: 178px;
margin: 100px;
}
.con {
display: none;
position: absolute;
top: -40px;
width: 171px;
border: 1px solid rgba(0, 0, 0, .2);
box-shadow: 0 2px 4px rgba(0, 0, 0, .2);
padding: 5px 0;
font-size: 18px;
line-height: 20px;
color: #333;
}
.con::before {
content: '';
width: 0;
height: 0;
position: absolute;
top: 28px;
left: 18px;
border: 8px solid #000;
border-style: solid dashed dashed;
border-color: #fff transparent transparent;
}
</style>
</head>
<body>
<div class="search">
<div class="con">123</div>
<input type="text" placeholder="请输⼊您的快递单号" class="jd">
</div>
<script>
// 快递单号输⼊内容时，上⾯的⼤号字体盒⼦（con）显⽰(这⾥⾯的字号更⼤）
// 表单检测⽤户输⼊：给表单添加键盘事件
// 同时把快递单号⾥⾯的值（value）获取过来赋值给 con盒⼦（innerText）做为内容
// 如果快递单号⾥⾯内容为空，则隐藏⼤号字体盒⼦(con)盒⼦
var con = document.querySelector('.con');
var jd_input = document.querySelector('.jd');
jd_input.addEventListener('keyup', function() {
// console.log('输⼊内容啦');
if (this.value == '') {
con.style.display = 'none';
} else {
con.style.display = 'block';
con.innerText = this.value;
}
})
// 当我们失去焦点，就隐藏这个con盒⼦
jd_input.addEventListener('blur', function() {
con.style.display = 'none';
})
// 当我们获得焦点，就显⽰这个con盒⼦
jd_input.addEventListener('focus', function() {
if (this.value !== '') {
con.style.display = 'block';
}
})
</script>
</body>
⼩编再为⼤家分享⼀段JS代码：
<script>
var inp = document.querySelector('.inp')
var son = document.querySelector('.son')
inp.addEventListener('keyup', function () {
if (this.value === '') {
son.style.visibility = 'hidden'
} else {
son.style.visibility = 'visible'
son.innerHTML = this.value
}
})
inp.addEventListener('blur', function () {
son.style.visibility = 'hidden'
})
inp.addEventListener('focus', function () {
快递收费标准if (this.value !== '') {
son.style.visibility = 'visible'
}
})
</script>
以上就是本⽂的全部内容，希望对⼤家的学习有所帮助，也希望⼤家多多⽀持。
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