JavaScript: Find the smallest prime number strictly greater than a given number

JavaScript Basic: Exercise-129 with Solution

Write a JavaScript program to find the smallest prime number strictly greater than a given number.

Visual Presentation:

Sample Solution:

JavaScript Code:

// Function to find the next prime number after a given number
function next_Prime_num(num) {
    // Start checking from the next number after 'num'
    for (var i = num + 1;; i++) {
        var isPrime = true;
        // Check divisibility from 2 up to the square root of the number
        for (var d = 2; d * d <= i; d++) {
            // If 'i' is divisible by 'd', it's not a prime number
            if (i % d === 0) {
                isPrime = false;
                break;
            }
        }
        // If 'isPrime' is still true, return 'i' (it's a prime number)
        if (isPrime) {
            return i;
        }
    }
}

// Test cases
console.log(next_Prime_num(3)); // Output: 5
console.log(next_Prime_num(17)); // Output: 19 

Output:

5
19

Live Demo:

See the Pen javascript-basic-exercise-129 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

// Function to find the next prime number after a given number
const next_Prime_num = (num) => {
    // Start checking from the next number after 'num'
    for (let i = num + 1;; i++) {
        let isPrime = true;
        // Check divisibility from 2 up to the square root of the number
        for (let d = 2; d * d <= i; d++) {
            // If 'i' is divisible by 'd', it's not a prime number
            if (i % d === 0) {
                isPrime = false;
                break;
            }
        }
        // If 'isPrime' is still true, return 'i' (it's a prime number)
        if (isPrime) {
            return i;
        }
    }
}

// Test cases
console.log(next_Prime_num(3)); // Output: 5
console.log(next_Prime_num(17)); // Output: 19

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