Frontend form validation

frontend-form-validation.markdown

Frontend form validation

A Pen by Chuks Festus on CodePen.

License.

index.html

<div class="container">
  <form class="registration" id="registration">
    <h1>Registration Form</h1>

    <label for="username">
				<span>Username</span>

				<input type="text" id="username" minlength="3" required>

				<ul class="input-requirements">
					<li>At least 3 characters long</li>
					<li>Must only contain letters and numbers (no special characters)</li>
				</ul>
			</label>

    <label for="password">
				<span>Password</span>

				<input type="password" id="password" maxlength="100" minlength="8" required>

				<ul class="input-requirements">
					<li>At least 8 characters long (and less than 100 characters)</li>
					<li>Contains at least 1 number</li>
					<li>Contains at least 1 lowercase letter</li>
					<li>Contains at least 1 uppercase letter</li>
					<li>Contains a special character (e.g. @ !)</li>
				</ul>
			</label>

    <label for="password_repeat">
				<span>Repeat Password</span>
				<input type="password" id="password_repeat" maxlength="100" minlength="8" required>
			</label>

    <br>

    <input type="submit">

  </form>
</div>

script.js

/* ----------------------------
	CustomValidation prototype
	- Keeps track of the list of invalidity messages for this input
	- Keeps track of what validity checks need to be performed for this input
	- Performs the validity checks and sends feedback to the front end
---------------------------- */

function CustomValidation(input) {
  this.invalidities = [];
  this.validityChecks = [];

  //add reference to the input node
  this.inputNode = input;

  //trigger method to attach the listener
  this.registerListener();
}

CustomValidation.prototype = {
  addInvalidity: function(message) {
    this.invalidities.push(message);
  },
  getInvalidities: function() {
    return this.invalidities.join('. \n');
  },
  checkValidity: function(input) {
    for (var i = 0; i < this.validityChecks.length; i++) {

      var isInvalid = this.validityChecks[i].isInvalid(input);
      if (isInvalid) {
        this.addInvalidity(this.validityChecks[i].invalidityMessage);
      }

      var requirementElement = this.validityChecks[i].element;

      if (requirementElement) {
        if (isInvalid) {
          requirementElement.classList.add('invalid');
          requirementElement.classList.remove('valid');
        } else {
          requirementElement.classList.remove('invalid');
          requirementElement.classList.add('valid');
        }

      } // end if requirementElement
    } // end for
  },
  checkInput: function() { // checkInput now encapsulated

    this.inputNode.CustomValidation.invalidities = [];
    this.checkValidity(this.inputNode);

    if (this.inputNode.CustomValidation.invalidities.length === 0 && this.inputNode.value !== '') {
      this.inputNode.setCustomValidity('');
    } else {
      var message = this.inputNode.CustomValidation.getInvalidities();
      this.inputNode.setCustomValidity(message);
    }
  },
  registerListener: function() { //register the listener here

    var CustomValidation = this;

    this.inputNode.addEventListener('keyup', function() {
      CustomValidation.checkInput();
    });

  }

};

/* ----------------------------
	Validity Checks
	The arrays of validity checks for each input
	Comprised of three things
		1. isInvalid() - the function to determine if the input fulfills a particular requirement
		2. invalidityMessage - the error message to display if the field is invalid
		3. element - The element that states the requirement
---------------------------- */

var usernameValidityChecks = [{
  isInvalid: function(input) {
    return input.value.length < 3;
  },
  invalidityMessage: 'This input needs to be at least 3 characters',
  element: document.querySelector('label[for="username"] .input-requirements li:nth-child(1)')
}, {
  isInvalid: function(input) {
    var illegalCharacters = input.value.match(/[^a-zA-Z0-9]/g);
    return illegalCharacters ? true : false;
  },
  invalidityMessage: 'Only letters and numbers are allowed',
  element: document.querySelector('label[for="username"] .input-requirements li:nth-child(2)')
}];

var passwordValidityChecks = [{
  isInvalid: function(input) {
    return input.value.length < 8 | input.value.length > 100;
  },
  invalidityMessage: 'This input needs to be between 8 and 100 characters',
  element: document.querySelector('label[for="password"] .input-requirements li:nth-child(1)')
}, {
  isInvalid: function(input) {
    return !input.value.match(/[0-9]/g);
  },
  invalidityMessage: 'At least 1 number is required',
  element: document.querySelector('label[for="password"] .input-requirements li:nth-child(2)')
}, {
  isInvalid: function(input) {
    return !input.value.match(/[a-z]/g);
  },
  invalidityMessage: 'At least 1 lowercase letter is required',
  element: document.querySelector('label[for="password"] .input-requirements li:nth-child(3)')
}, {
  isInvalid: function(input) {
    return !input.value.match(/[A-Z]/g);
  },
  invalidityMessage: 'At least 1 uppercase letter is required',
  element: document.querySelector('label[for="password"] .input-requirements li:nth-child(4)')
}, {
  isInvalid: function(input) {
    return !input.value.match(/[\!\@\#\$\%\^\&\*]/g);
  },
  invalidityMessage: 'You need one of the required special characters',
  element: document.querySelector('label[for="password"] .input-requirements li:nth-child(5)')
}];

var passwordRepeatValidityChecks = [{
  isInvalid: function() {
    return passwordRepeatInput.value != passwordInput.value;
  },
  invalidityMessage: 'This password needs to match the first one'
}];

/* ----------------------------
	Setup CustomValidation
	Setup the CustomValidation prototype for each input
	Also sets which array of validity checks to use for that input
---------------------------- */

var usernameInput = document.getElementById('username');
var passwordInput = document.getElementById('password');
var passwordRepeatInput = document.getElementById('password_repeat');

usernameInput.CustomValidation = new CustomValidation(usernameInput);
usernameInput.CustomValidation.validityChecks = usernameValidityChecks;

passwordInput.CustomValidation = new CustomValidation(passwordInput);
passwordInput.CustomValidation.validityChecks = passwordValidityChecks;

passwordRepeatInput.CustomValidation = new CustomValidation(passwordRepeatInput);
passwordRepeatInput.CustomValidation.validityChecks = passwordRepeatValidityChecks;

/* ----------------------------
	Event Listeners
---------------------------- */

var inputs = document.querySelectorAll('input:not([type="submit"])');

var submit = document.querySelector('input[type="submit"');
var form = document.getElementById('registration');

function validate() {
  for (var i = 0; i < inputs.length; i++) {
    inputs[i].CustomValidation.checkInput();
  }
}

submit.addEventListener('click', validate);
form.addEventListener('submit', validate);

style.css

/* FormHack v1.2.0 (formhack.io) */

/* Config ----------------------------- */
:root {

  /* Font */
  --fh-font-family: 'Source Sans Pro', sans-serif;
  --fh-font-size: 15px;
  --fh-font-color: rgb(40, 40, 40);

  /* Borders */
  --fh-border-radius: 3px;
  --fh-border-width: 1px;
  --fh-border-style: solid;
  --fh-border-color: rgb(200, 200, 200);

  /* Inputs, Textareas, Select, Option */
  --fh-input-height: 40px;
  --fh-input-width: 100%;
  --fh-input-max-width: 400px;
  --fh-input-bg-color: rgb(250,250,250);
  --fh-focus-bg-color: var(--fh-input-bg-color);
  --fh-focus-border-color: #000;
  --fh-focus-font-color: var(--fh-font-color);

  /* Select Vendor Styling */
  --fh-select-vendor-styling: none; /* comment this out to maintain vendor styling */


  /* Buttons & Input Submits */
  --fh-button-height: 40px;
  --fh-button-width: 100%;
  --fh-button-max-width: 200px;
  --fh-button-font-color: var(--fh-font-color);
  --fh-button-bg-color: rgba(255, 219, 58,0.3);
  --fh-button-hover-bg-color: rgb(255, 219, 58);
  --fh-button-hover-font-color: var(--fh-font-color);

  /* Layout */
  --fh-layout-display: block;
  --fh-layout-margin: 10px auto; /* change to "10px auto" to center */
  --fh-layout-text-align: center;
}



/* Global Reset Styles ------------------ */



input,
textarea,
select,
option,
optgroup,
button,
legend,
fieldset {
  box-sizing: border-box;
  outline: none;

  font-family: var(--fh-font-family);
  font-size: var(--fh-font-size);
  color: var(--fh-font-color);
  vertical-align: top;

  display: var(--fh-layout-display);
  margin: var(--fh-layout-margin);
  text-align: var(--fh-layout-text-align);
}


datalist {
  font-family: var(--fh-font-family);
  font-size: var(--fh-font-size);
}

label {
  display: block;
  margin: var(--fh-layout-margin);
  text-align: var(--fh-layout-text-align);
  margin-bottom: 20px;
  position: relative;
  padding: 0 20px;
}



/* Input & Textarea ------------------ */

/* Fields with standard width */
input[type="text"],
input[type="email"],
input[type="password"],
input[type="search"],
input[type="color"],
input[type="date"],
input[type="datetime-local"],
input[type="month"],
input[type="number"],
input[type="tel"],
input[type="time"],
input[type="url"],
input[type="week"],
input[list],
input[type="file"],
select,
textarea {
  width: var(--fh-input-width);
  max-width: var(--fh-input-max-width);
  padding: calc( var(--fh-input-height) / 5 );
  background-color: var(--fh-input-bg-color);

  border-radius: var(--fh-border-radius);
  border-width: var(--fh-border-width);
  border-style: var(--fh-border-style);
  border-color: var(--fh-border-color);
}

/* Fields with standard height */
input[type="text"],
input[type="email"],
input[type="password"],
input[type="search"],
input[type="color"],
input[type="date"],
input[type="datetime-local"],
input[type="month"],
input[type="number"],
input[type="tel"],
input[type="time"],
input[type="url"],
input[type="week"],
input[list] {
  height: var(--fh-input-height);
  -webkit-appearance: none;
}

/* Other */

textarea {
  -webkit-appearance: none;
  overflow: auto;
}

input[type="range"] {
  height: var(--fh-input-height);
  width: var(--fh-input-width);
  max-width: var(--fh-input-max-width);
}

input[type="file"] {
  min-height: var(--fh-input-height);
}

input[type="search"] {
  height: var(--fh-input-height);
  -webkit-appearance: none;
}
input[type="search"]::-webkit-search-cancel-button,
input[type="search"]::-webkit-search-decoration {
  -webkit-appearance: none;
}

input[type="checkbox"],
input[type="radio"] {
  display: inline-block;
  vertical-align: middle;
}
/* For checkbox and radio to be centered, need to wrap the input and label in a span -
/* .checkbox-container {
/*  display: block;
/*  text-align: center;
/* }
/* Select ------------------ */

select {
  height: var(--fh-input-height);

  -webkit-appearance: var(--fh-select-vendor-styling, menulist);
  -moz-appearance: var(--fh-select-vendor-styling, menulist);
  -ms-appearance: var(--fh-select-vendor-styling, menulist);
  -o-appearance: var(--fh-select-vendor-styling, menulist);


}

select[multiple] {
  height: auto;
  min-height: var(--fh-input-height);
  padding: 0;
}

select[multiple] option {
  margin: 0;
  padding: calc( var(--fh-input-height) / 5 );
}

/* Fieldset ------------------ */

fieldset {
  padding: 0;
  border: 0;
}

legend {
  padding: 0;
  font-weight: inherit;
}

/* Buttons, Input Type Submit/Reset ------------------ */

button,
input[type="button"],
input[type="submit"],
input[type="reset"],
input[type="image"] {
  height: var(--fh-button-height);
  width: var(--fh-button-width);
  max-width: var(--fh-button-max-width);
  background-color: var(--fh-button-bg-color);
  padding: calc( var(--fh-input-height) / 5 );
  cursor: pointer;

  color: var(--fh-button-font-color);
  font-weight: 700;

  -webkit-appearance: none;
  -moz-appearance: none;

  border-radius: var(--fh-border-radius);
  border-width: var(--fh-border-width);
  border-style: var(--fh-border-style);
  border-color: var(--fh-border-color);



  box-shadow: 1px 1px 5px 0px rgba(0,0,0,0.2);
}

input[type="image"] {
  text-align: center;
  padding: calc( var(--fh-input-height) / 5 );
}

/* States ------------------ */

input[disabled],
textarea[disabled],
select[disabled],
option[disabled],
button[disabled] {
  cursor: not-allowed;
}

input:focus,
textarea:focus,
select:focus,
option:focus,
button:focus  {
  background-color: var(--fh-focus-bg-color);
  border-color: var(--fh-focus-border-color);
}

input[type="checkbox"]:focus,
input[type="radio"]:focus {
  outline: var(--fh-focus-border-color) solid 2px;
}

button:hover,
input[type="button"]:hover,
input[type="submit"]:hover,
input[type="reset"]:hover,
button:focus,
input[type="button"]:focus,
input[type="submit"]:focus,
input[type="reset"]:focus {
  background-color: var(--fh-button-hover-bg-color);
  color: var(--fh-button-hover-font-color);
}




/* Custom ------------------ */


input:not([type="submit"]):valid {
  border-color: #2ecc71;
}


/* Hide and show related .input-requirements when interacting with input */

input:not([type="submit"]) + .input-requirements {
  overflow: hidden;
  max-height: 0;
  transition: max-height 1s ease-out;  
}

input:not([type="submit"]):hover + .input-requirements,
input:not([type="submit"]):focus + .input-requirements,
input:not([type="submit"]):active + .input-requirements {
  max-height: 1000px; /* any large number (bigger then the .input-requirements list) */
  transition: max-height 1s ease-in;
}

/* RESET */

html,
body,
div,
span,
applet,
object,
iframe,
h1,
h2,
h3,
h4,
h5,
h6,
p,
blockquote,
pre,
a,
abbr,
acronym,
address,
big,
cite,
code,
del,
dfn,
em,
img,
ins,
kbd,
q,
s,
samp,
small,
strike,
strong,
sub,
sup,
tt,
var,
b,
u,
i,
center,
dl,
dt,
dd,
ol,
ul,
li,
fieldset,
form,
label,
legend,
table,
caption,
tbody,
tfoot,
thead,
tr,
th,
td,
article,
aside,
canvas,
details,
embed,
figure,
figcaption,
footer,
header,
hgroup,
menu,
nav,
output,
ruby,
section,
summary,
time,
mark,
audio,
video {
  margin: 0;
  padding: 0;
  border: 0;
  font: inherit;
  font-size: 100%;
  vertical-align: baseline;
}

article,
aside,
details,
figcaption,
figure,
footer,
header,
hgroup,
menu,
nav,
section {
  display: block;
}

ul {
  list-style: none;
}

blockquote,
q {
  quotes: none;
}

blockquote:before,
blockquote:after,
q:before,
q:after {
  content: '';
  content: none;
}

table {
  border-collapse: collapse;
  border-spacing: 0;
}

html {
  box-sizing: border-box;
}

*,
*:before,
*:after {
  box-sizing: inherit;
}

html {
  font-size: 62.5%;
}

body {
  font-size: 1.6rem;
  line-height: 1.6;
  font-family: 'Source Sans Pro';
  background-color: rgb(245, 245, 245);
}

h1 {
  font-size: 2.5rem;
  padding: 15px 20px;
  background-color: rgba(255, 219, 58, 0.3);
  margin-bottom: 20px;
  text-align: center;
}

a {
  text-decoration: underline;
  color: inherit;
}

.container {
  margin: 80px auto;
  width: 90%;
  max-width: 800px;
}

.registration {
  background-color: #fff;
  max-width: 600px;
  margin: 0 auto;
  padding-bottom: 20px;
  box-shadow: 1px 1px 5px 0px rgba(0, 0, 0, 0.3);
  border-bottom: 5px solid #ffdb3a;
}

.input-requirements {
  font-size: 1.3rem;
  font-style: italic;
  text-align: left;
  list-style: disc;
  list-style-position: inside;
  max-width: 400px;
  margin: 10px auto;
  color: rgb(150, 150, 150);
}

.input-requirements li.invalid {
  color: #e74c3c;
}

.input-requirements li.valid {
  color: #2ecc71;
}

.input-requirements li.valid:after {
  display: inline-block;
  padding-left: 10px;
  content: "\2713";
}