A simple program that I wrote to check if the number given by the user is a prime number or not. I also added a functionality that will check if the given value is an invalid entry like letters or special characters.
If you have some questions please send me an email at jake.r.pomperada@gmail.com and jakerpomperada@yahoo.com. My mobile number here in the Philippines is 09173084360.
Sample Program Output
Program Listing
<html>
<head>
<style>
body {
background-color:lightgreen;
font-family:arial;
font-size:25px;
color:blue;
}
label {
float: left;
width: 30%;
text-align: left;
margin-right: 1em;
white-space: nowrap;
overflow: hidden;
text-overflow: ellipsis;
-o-text-overflow: ellipsis;
}
.form-field-no-caption {
margin-le
input[type="radio"]{
float:left;
}
</style>
<meta charset="UTF-8">
<title>Prime Number Checker in JavaScript</title>
<script type="text/javascript">
function check_prime() {
var input = document.getElementById("userInput").value;
var number = parseInt(input);
if (isNaN(number)) {
alert("Please enter a number.");
document.getElementById("userInput").value="";
document.getElementById("result").innerHTML = "";
document.getElementById("userInput").focus();
}
else if (input.length === 0) {
alert("Please enter a valid input");
document.getElementById("userInput").focus();
}
else if (!isNaN(number)) {
if (isPrime(number)) {
document.getElementById("result").innerHTML = number + " is a PRIME number.";
}
else {
document.getElementById("result").innerHTML = number + " is NOT a PRIME number.";
}
}
else {
document.getElementById("result").innerHTML = "Please enter a number.";
}
}
function isPrime(n_value) {
if (n_value < 2) {
return false
}
if (n_value != Math.round(n_value)) {
return false
}
var isPrime = true;
for (var i = 2; i <= Math.sqrt(n_value); i++) {
if (n_value % i == 0) {
isPrime = false
}
}
return isPrime;
}
function clear_textbox(){
document.getElementById("result").innerHTML = "";
document.getElementById("userInput").value="";
document.getElementById("userInput").focus();
}
</script>
</head>
<body>
<h2> Prime Number Checker in JavaScript </h2>
Enter a Number
<input type="text" id="userInput" autofocus value = "" />
<input type="submit" value="Check"
title="Click here to check if the given number is an prime number or not."
onclick="check_prime()" />
<input type="submit" value="Clear"
title="Click here to clear the text box."
onclick="clear_textbox()" />
<br><br>
<p id="result"></h1>
</body>
</html>
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