username page javascript validation

Question

Could anyone help with this?

Code allowing the user to input a username and a password, both of which must be validated as follows:

The username may only contain letters, dots (.), the at sign (@). The username must NOT be longer than 25 characters.

I'm afraid you cannot ask a question which shows no previous research or effort, you are essentially asking people to do your work for you, and you will learn nothing by doing this. Read this: https://stackoverflow.com/questions/1221985/how-to-validate-a-user-name-with-regex — Panomosh, Apr 17 '18 at 10:25
You can either use a custom library like jQuery Validate https://jqueryvalidation.org/validate/ or learn how to create validation using REGEX — Panomosh, Apr 17 '18 at 10:27
Please. Upload some snippet showing but you have done so far. — goediaz, Apr 17 '18 at 10:53

score 0 · Answer 1 · answered Apr 17 '18 at 10:48

In order to limit to 25 characters, the easiest way is to use an

<input type="text" maxlength="25" />

In order to validate that input only contains letters, dots (.) and @, proceed with a regular expression.

Example:

<input id="input" type="text" maxlength="25" />
<button id="button">Test</button>
<br/>
<div id="validation" />


$(document).ready(function(){
   var $text = $('#input');
   var $btn  = $('#button');
   var $out  = $('#validation');

   $btn.on('click', _do_check);

  function _do_check(e){
    e.preventDefault();
    e.stopPropagation();

    var text = $text.val();

    if (/^[a-zA-Z.@]+$/.test(text) ){
      $out.html('OK');
    } else {
      $out.html('FAILURE');
    }    
  }
});

Hope this helps.

score 0 · Answer 2 · answered Apr 17 '18 at 10:58

Using only plain Javascript:

You will need to construct a regular expression. Check this to get an idea how it works in Javascript https://www.w3schools.com/jsref/jsref_obj_regexp.asp

The following expression would be a regular expression fitting your username requirements with the only allowed characters and the length restrictions at once

/^([a-zA-Z\.\@]{1,25})$/

You can play and learn how to build a regular expression with pages like https://regexr.com/

And as recommended you should start with some of your work in order to help actually with a problem and then the community can guide you to solve your real issue.

username page javascript validation

2 Answers2