JSFiddle - React, Tailwind, and code Playground

Username and Password

by David Lomneck

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/semantic-ui/2.2.4/semantic.min.css">
<div class="ui container">
  <div class="ui form error">
    <div class="field error">
      <label>Username</label>
      <input type="text" placeholder="Username" id="inputUsername">
    </div>
    <div class="field error">
      <label>Password</label>
      <input type="text" placeholder="Password" id="inputPassword">
    </div>
    <div class="ui error message">
      <div class="header">Something is invalid...</div>
      <p id="errorMessage"></p>
    </div>
  </div>
</div>

JavaScript

//
// Complete implementations of the validateUsername and validatePassword functions
// throwing errors when invalid. You may use: https://developer.mozilla.org if you need help with syntax
// https://getfirebug.com/firebug-lite-debug.js as external resource for a build-in console window


// A valid username is at least 6 characters long
// A valid username cannot be longer than 20 characters
function validateUsername(username) {
  	throw 'Username is not valid!';
}


// A Valid password must be at least 8 characters long
// A Valid password cannot be longer than 30 characters
// A valid password must contain at least 1 number
function validatePassword(password) {
  throw 'Password is not valid!';
}





// You can ignore everything below this comment
(function() {
  var elements = {
    username: document.getElementById('inputUsername'),
    password: document.getElementById('inputPassword'),
    errorMessage: document.getElementById('errorMessage'),
    form: document.getElementsByClassName('ui form')[0]
  };
  var errors = {};

  wireup(elements.username, validateUsername);
  wireup(elements.password, validatePassword);

  function wireup(element, callback) {
    element.addEventListener('input', function(e) {
      try {
        callback(element.value);
        element.parentElement.classList.remove('error');
        delete errors[element.id];
      } catch (e) {
        element.parentElement.classList.add('error');
        errors[element.id] = e;
      }
      var fieldsInError = Object.keys(errors);
      if(fieldsInError.length == 0){
      	elements.form.classList.remove('error');
      } else {
      	errorMessage.innerText = fieldsInError.map(function(e){ return errors[e]; }).join('\r');
      	elements.form.classList.add('error');
      }
    });
  }
})();