JavaScript: Sort an array of all prime numbers between 1 and a given integer

JavaScript Basic: Exercise-109 with Solution

Write a JavaScript program to sort an array of all prime numbers between 1 and a given integer.

Sample Solution:

JavaScript Code:

// Function to sort prime numbers up to 'num'
function sort_prime(num) {
  var prime_num1 = [], // Array to store prime numbers
      prime_num2 = []; // Array to track prime status (true/false)

  // Initialize prime_num2 array to true for all indices from 0 to num
  for (var i = 0; i <= num; i++) {
    prime_num2.push(true);
  }

  // Loop to find prime numbers using the Sieve of Eratosthenes algorithm
  for (var i = 2; i <= num; i++) {
    if (prime_num2[i]) {
      prime_num1.push(i); // Push the current number to prime_num1 if it's a prime

      // Mark multiples of the current number as non-prime in prime_num2
      for (var j = 1; i * j <= num; j++) {
        prime_num2[i * j] = false;
      }
    }
  }

  return prime_num1; // Return the array containing sorted prime numbers
}

// Example usage of the sort_prime function with different values
console.log(sort_prime(5)); // Output: [2, 3, 5]
console.log(sort_prime(11)); // Output: [2, 3, 5, 7, 11]
console.log(sort_prime(19)); // Output: [2, 3, 5, 7, 11, 13, 17, 19]

Output:

[2,3,5]
[2,3,5,7,11]
[2,3,5,7,11,13,17,19]

Live Demo:

See the Pen javascript-basic-exercise-109 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

// Function to sort prime numbers up to a given number
const sort_prime = (num) => {
  let prime_num1 = []; // Array to store prime numbers
  let prime_num2 = []; // Array to hold flags indicating prime numbers

  // Initializing flags in prime_num2 array
  for (let i = 0; i <= num; i++) {
    prime_num2.push(true);
  }

  // Finding prime numbers using the Sieve of Eratosthenes algorithm
  for (let i = 2; i <= num; i++) {
    if (prime_num2[i]) {
      prime_num1.push(i); // Pushing the prime number to the prime_num1 array
      // Marking multiples of the current prime number as non-prime in prime_num2
      for (let j = 1; i * j <= num; j++) {
        prime_num2[i * j] = false;
      }
    }
  }

  return prime_num1; // Returning the sorted array of prime numbers
};

// Example usage of the function
console.log(sort_prime(5)); // Output: [2, 3, 5] (prime numbers up to 5)
console.log(sort_prime(11)); // Output: [2, 3, 5, 7, 11] (prime numbers up to 11)
console.log(sort_prime(19)); // Output: [2, 3, 5, 7, 11, 13, 17, 19] (prime numbers up to 19)

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