l100/formulier.php

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        window.onload = function(){
            document.getElementById('check').onclick = check;
            check();
        }
        function check(){
            if(document.getElementById('check').checked){
               document.getElementById('tussenv').style.display ='block';
            }
            else{
                document.getElementById('tussenv').style.display ='none';
            }
        }
    </script>
    <style>
        span{
            width:100px;
            display:inline-block;
            text-align:left;
        }
        
    </style>
</head>
<body>
    
     <form action="" method="get">
            <div><span>Voornaam:</span><input type="text" name="voornaam"></input></div>
            <div><span>Achternaam:</span><input type="text" name="achternaam"></input></div>
            <div><input type="checkbox" name="tussenvoegsel" id="check"><label for="tussenvoegsel">Mijn naam bevat een tussenvoegsel</label></input></div>
            <div id="tussenv"><div><span>tussenvoegsel:</span><input type="text" name="tussenv"></input></div>
        </form>
</body>
</html>

Resultaat

Made by Thijs Aarnoudse