Check Empty String with JavaScript
01/29/2021
Contents
Demo
Code
HTML
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<title>Check Empty String with JavaScript</title>
<link rel="stylesheet" type="text/css" href="https://demo.plantpot.works/assets/css/normalize.css">
<link rel="stylesheet" href="https://use.typekit.net/opg3wle.css">
<link rel="stylesheet" type="text/css" href="style.css">
<script src="validation.js"></script>
</head>
<body>
<div id="container">
<form id="form" class="form" name="form" action="#" method="post">
<div class="form-input-box">
<input id="form-input" class="form-input" type="text" name="text" placeholder="Enter text" oninput="checkString()">
<p id="msg" class="msg"></p>
</div>
</form>
</div>
</body>
</html>
CSS
@charset "utf-8";
* {
box-sizing: border-box;
margin: 0;
padding: 0;
}
html {
font-size: 16px;
}
body {
background-color: #f5f6e7;
font-family: futura-pt, sans-serif;
-webkit-tap-highlight-color: rgba(0,0,0,0);
}
#container {
display: flex;
justify-content: center;
align-items: center;
position: relative;
width: 100%;
height: 100vh;
}
.form {
width: 100%;
max-width: 450px;
padding: 20px;
}
.form-input-box {
position: relative;
}
.form-input {
width: 100%;
padding: 15px 10px;
border: 1px solid #3d3935;
border-radius: 4px;
background-color: #fff;
color: #3d3935;
font-size: 1.125rem;
outline: 0;
}
.form-input::placeholder {
color: #ccc;
font-size: 1.125rem;
}
.msg {
position: absolute;
bottom: -30px;
left: 0;
font-size: 1.125rem;
}
.invalid .msg {
color: #bf0404;
}
.valid .form-input {
border: 1px solid #23b08d;
background-image: url("valid.svg");
background-position: 98%;
background-size: 20px 20px;
background-repeat: no-repeat;
}
.invalid .form-input {
border: 1px solid #bf0404;
background-image: url("invalid.svg");
background-position: 98%;
background-size: 20px 20px;
background-repeat: no-repeat;
}
JavaScript
function checkString() {
var form = document.getElementById("form");
var str = document.getElementById("form-input").value;
var msg = document.getElementById("msg");
if(str === "") {
form.classList.remove("valid");
form.classList.add("invalid");
msg.innerHTML = "This field is required.";
}
else {
form.classList.remove("invalid");
form.classList.add("valid");
msg.innerHTML = "";
}
}