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

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2021-03-30 15:38:2811731browse

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

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>

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;;
?>

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>

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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