feat: Add prime number checker in Javascript

javascript/README.md

@@ -1,4 +1,3 @@
 # Javascript
 
-- hello_world.js | 2024-01-01 | 1 line
-- prime_number_finder.js | 2024-07-31 | 28 lines
+- prime-number-finder.js | 2025-12-28 | 26 lines

javascript/package.json

@@ -2,7 +2,7 @@
   "name": "javascript-programs",
   "version": "1.0.0",
   "description": "A collection of Javascript programs.",
-  "main": "index.js",
+  "main": "prime-number-finder.js",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1"
   },

javascript/prime-number-finder.js

@@ -0,0 +1,26 @@
+#!/usr/bin/env node
+
+function isPrime(num) {
+  if (num <= 1) return false;
+  if (num <= 3) return true;
+
+  if (num % 2 === 0 || num % 3 === 0) return false;
+
+  for (let i = 5; i * i <= num; i = i + 6) {
+    if (num % i === 0 || num % (i + 2) === 0) return false;
+  }
+
+  return true;
+}
+
+const number = parseInt(process.argv[2]);
+
+if (isNaN(number)) {
+  console.log('Please provide a valid number.');
+} else {
+  if (isPrime(number)) {
+    console.log(`${number} is a prime number.`);
+  } else {
+    console.log(`${number} is not a prime number.`);
+  }
+}