JavaScript: Check whether the provided integer is a prime number or not

JavaScript fundamental (ES6 Syntax): Exercise-191 with Solution

Check If Prime Number

Write a JavaScript program to check if the provided integer is a prime number or is not.

• Check numbers from 2 to the square root of the given number.
• Return false if any of them divides the given number, else return true, unless the number is less than 2.

Sample Solution:

JavaScript Code:

// Define a function 'isPrime' that checks if the given number 'num' is a prime number
const isPrime = num => {
  // Define the boundary as the square root of the number rounded down to the nearest integer
  const boundary = Math.floor(Math.sqrt(num));
  // Iterate through numbers from 2 to the square root of 'num'
  for (var i = 2; i <= boundary; i++)
    // If 'num' is divisible by 'i' with no remainder, it's not a prime number, return false
    if (num % i === 0) return false;
  // Return true if 'num' is greater than or equal to 2, otherwise return false
  return num >= 2;
};

// Test cases to check if the numbers are prime
console.log(isPrime(11)); // true (11 is a prime number)
console.log(isPrime(17)); // true (17 is a prime number)
console.log(isPrime(8)); // false (8 is not a prime number)

Output:

true
true
false

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-191-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that determines if a given integer is prime by testing divisibility up to its square root.
• Write a JavaScript function that efficiently checks for prime status using optimized iteration and early exit.
• Write a JavaScript program that validates a number as prime and handles edge cases like 0, 1, and negative numbers.
• Write a JavaScript function that uses recursion or iterative loops to check for factors of a number.

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