Claim:
When the user enters content in the input box, the large font box above is condisplayed (the font size is larger)
Realization ideas:
- Form detection user input: add keyboard events to the form
- At the same time, get the value in the courier number
valueand assign it to theconboxinnerTextas the content - If the content of the courier number is empty, hide the large font
conbox
Code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<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>
var con = document.querySelector('.con');
var jd_input = document.querySelector('.jd');
jd_input.addEventListener('keyup', function() {
if (this.value == '') {
con.style.display = 'none';
} else {
con.style.display = 'block';
con.innerText = this.value;
}
});
// 当失去焦点，就隐藏这个con盒子
jd_input.addEventListener('blur', function() {
con.style.display = 'none';
});
// 当获得焦点，就显示这个con盒子
jd_input.addEventListener('focus', function() {
if (this.value !== '') {
con.style.display = 'block';
}
});
</script>
</body>
</html>