In this JavaScript guide, our focus will be on implementing client-side form validation using JavaScript. Additionally, we will explore two distinct input styles: success and error, which represent various states that inputs can assume.
Source Code
<div class="container">
<div class="header">
<h2>Create Account</h2>
</div>
<form id="form" class="form">
<div class="form-control">
<label for="username">Username</label>
<input type="text" placeholder="florinpop17" id="username" />
<i class="fas fa-check-circle"></i>
<i class="fas fa-exclamation-circle"></i>
<small>Error message</small>
</div>
<div class="form-control">
<label for="username">Email</label>
<input type="email" placeholder="a@florin-pop.com" id="email" />
<i class="fas fa-check-circle"></i>
<i class="fas fa-exclamation-circle"></i>
<small>Error message</small>
</div>
<div class="form-control">
<label for="username">Password</label>
<input type="password" placeholder="Password" id="password"/>
<i class="fas fa-check-circle"></i>
<i class="fas fa-exclamation-circle"></i>
<small>Error message</small>
</div>
<div class="form-control">
<label for="username">Password check</label>
<input type="password" placeholder="Password two" id="password2"/>
<i class="fas fa-check-circle"></i>
<i class="fas fa-exclamation-circle"></i>
<small>Error message</small>
</div>
<button>Submit</button>
</form>
</div>
@import url('https://fonts.googleapis.com/css?family=Muli&display=swap');
@import url('https://fonts.googleapis.com/css?family=Open+Sans:400,500&display=swap');
* {
box-sizing: border-box;
}
body {
background-color: #9b59b6;
font-family: 'Open Sans', sans-serif;
display: flex;
align-items: center;
justify-content: center;
min-height: 100vh;
margin: 0;
}
.container {
background-color: #fff;
border-radius: 5px;
box-shadow: 0 2px 5px rgba(0, 0, 0, 0.3);
overflow: hidden;
width: 400px;
max-width: 100%;
}
.header {
border-bottom: 1px solid #f0f0f0;
background-color: #f7f7f7;
padding: 20px 40px;
}
.header h2 {
margin: 0;
}
.form {
padding: 30px 40px;
}
.form-control {
margin-bottom: 10px;
padding-bottom: 20px;
position: relative;
}
.form-control label {
display: inline-block;
margin-bottom: 5px;
}
.form-control input {
border: 2px solid #f0f0f0;
border-radius: 4px;
display: block;
font-family: inherit;
font-size: 14px;
padding: 10px;
width: 100%;
}
.form-control input:focus {
outline: 0;
border-color: #777;
}
.form-control.success input {
border-color: #2ecc71;
}
.form-control.error input {
border-color: #e74c3c;
}
.form-control i {
visibility: hidden;
position: absolute;
top: 40px;
right: 10px;
}
.form-control.success i.fa-check-circle {
color: #2ecc71;
visibility: visible;
}
.form-control.error i.fa-exclamation-circle {
color: #e74c3c;
visibility: visible;
}
.form-control small {
color: #e74c3c;
position: absolute;
bottom: 0;
left: 0;
visibility: hidden;
}
.form-control.error small {
visibility: visible;
}
.form button {
background-color: #8e44ad;
border: 2px solid #8e44ad;
border-radius: 4px;
color: #fff;
display: block;
font-family: inherit;
font-size: 16px;
padding: 10px;
margin-top: 20px;
width: 100%;
}
const form = document.getElementById('form');
const username = document.getElementById('username');
const email = document.getElementById('email');
const password = document.getElementById('password');
const password2 = document.getElementById('password2');
form.addEventListener('submit', e => {
e.preventDefault();
checkInputs();
});
function checkInputs() {
// trim to remove the whitespaces
const usernameValue = username.value.trim();
const emailValue = email.value.trim();
const passwordValue = password.value.trim();
const password2Value = password2.value.trim();
if(usernameValue === '') {
setErrorFor(username, 'Username cannot be blank');
} else {
setSuccessFor(username);
}
if(emailValue === '') {
setErrorFor(email, 'Email cannot be blank');
} else if (!isEmail(emailValue)) {
setErrorFor(email, 'Not a valid email');
} else {
setSuccessFor(email);
}
if(passwordValue === '') {
setErrorFor(password, 'Password cannot be blank');
} else {
setSuccessFor(password);
}
if(password2Value === '') {
setErrorFor(password2, 'Password2 cannot be blank');
} else if(passwordValue !== password2Value) {
setErrorFor(password2, 'Passwords does not match');
} else{
setSuccessFor(password2);
}
}
function setErrorFor(input, message) {
const formControl = input.parentElement;
const small = formControl.querySelector('small');
formControl.className = 'form-control error';
small.innerText = message;
}
function setSuccessFor(input) {
const formControl = input.parentElement;
formControl.className = 'form-control success';
}
function isEmail(email) {
return /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/.test(email);
}
•setErrorFor()
The setErrorFor() function is used to update appearance of a form control to indicate an error. It takes two parameters: input element and an error message. It starts by getting parent element of input and finding small element inside it. It then sets class of parent element to 'form-control error' to apply error style and sets inner text of small element to error message.
•setSuccessFor()
This function is used to update appearance of a form control to indicate a successful input. It takes one parameter, input element. It starts by getting parent element of input and sets class of parent element to 'form-control success' to apply success style.
•isEmail()
The isEmail() function that uses a regular expression pattern to check if input string is a valid email address. The regular expression pattern used in this function is quite complex, but it essentially checks if input string matches format of a valid email address. If input string matches format of a valid email address, function returns true. If input string does not match format of a valid email address, function returns false.
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