The onblur event and onfocus are relative events. When the cursor leaves the currently focused object, the onblur event is triggered and the called program is executed at the same time.
Look at the following code:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>失去焦点事件</title>
</head>
<body>
<form>
请输入你的身份证号：<input type="text" onblur="onf()">
</form>
<script type="text/javascript">
function onf(){
alert('请输入用户名');
}
</script>
</body>
</html>When the text When the box loses focus, "Please enter username" will pop up
Next Section