regex for username
let username = '';
username = username.replace(/\s/g,'_');
username = username.replace(/\-/g,'.');
username = username.match(/[a-zA-Z0-9\.\s]+/g).join('_');regex for username
let username = '';
username = username.replace(/\s/g,'_');
username = username.replace(/\-/g,'.');
username = username.match(/[a-zA-Z0-9\.\s]+/g).join('_');username regex
^(?=[a-zA-Z0-9._]{8,20}$)(?!.*[_.]{2})[^_.].*[^_.]$regex for username
# works in most newer browsers
^(?=.{8,20}$)(?![_.])(?!.*[_.]{2})[a-zA-Z0-9._]+(?<![_.])$
└─────┬────┘└───┬──┘└─────┬─────┘└─────┬─────┘ └───┬───┘
│ │ │ │ no _ or . at the end
│ │ │ │
│ │ │ allowed characters
│ │ │
│ │ no __ or _. or ._ or .. inside
│ │
│ no _ or . at the beginning
│
username is 8-20 characters long
# works in all browsers, but does the same as the above RegEx
^(?=[a-zA-Z0-9._]{8,20}$)(?!.*[_.]{2})[^_.].*[^_.]$username validation
<html>
<head>
<title></title>
</head>
<body>
<form method="post" action="">
username:<input type="text" id="name" onkeyup="validation()">
</form>
</body>
<script type="text/javascript">
function validation(){
var username=document.getElementById("name").value;///get id with value
var usernamepattern=/^[A-Za-z .]{3,15}$/;////Regular expression
if(usernamepattern.test(username))
{
document.getElementById("name").style.backgroundColor='yellow';
}
else
{
document.getElementById("name").style.backgroundColor='red'; }
}
</script>
</html>Copyright © 2021 Codeinu
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