How to determine whether the content of the text box in html is empty-HTML Tutorial-php.cn

How to determine whether the content of the text box in html is empty

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Release： 2021-04-15 14:05:44

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There are many ways to determine whether the content of the text box in the form is empty: 1. Judge through the php statement 2. Through js Statement judgment 3. Judge through html native statements.

1. Determine through the PHP statement:

Content in html:

<form action="submit.php" method="post">
<textarea name="text"></textarea>
</form>

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Content in php:

//submit.php
<?php
if(isset($_POST[&#39;text&#39;]) && strlen(trim($_POST[&#39;text&#39;]))>0)
echo &#39;不空&#39;;
else
echo &#39;空 &#39;;
?>

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2. Judgment by JS statement

<html>
<head>
<title>JS判断input是否为空</title>
<script>function op(){
	if(document.getElementById("ip").value==""){
		alert("input为空");
	}else{
		alert(document.getElementById("ip").value);
	}
	}
</script>
</head>
<body>
    <input id="ip" onblur="op()" value="JS"/>
</body>
</html>

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3. Judgment by requiredattribute

<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>表单</title>
</head>
<body>
    <form action="" style="display: grid;" method="POST">
     
    <div>

        <label for="username">账号：</label>
        <input type="text" id="username" required> 
                                 <!--required为必须填写数据-->
    </div>
</body>
</html>

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