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May 2, 2022 19:52
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freeCodeCamp: Sum All Primes Solution
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| // A prime number is a whole number greater than 1 with exactly two divisors: 1 and itself. | |
| // For example, 2 is a prime number because it is only divisible by 1 and 2. | |
| // In contrast, 4 is not prime since it is divisible by 1, 2 and 4. | |
| // Rewrite sumPrimes so it returns the sum of all prime numbers that are less than or equal to num. | |
| function sumPrimes(num) { | |
| let primeArr = []; | |
| for(let i = 2; i <= num; i++) { | |
| if(primeArr.every((prime) => i % prime !== 0)) | |
| primeArr.push(i); | |
| } | |
| return primeArr.reduce((sum, prime) => sum + prime, 0); | |
| } | |
| // Another Solution Using JS Math Object | |
| function sumPrimes(num) { | |
| // Helper function to check primality | |
| function isPrime(num) { | |
| for (let i = 2; i <= Math.sqrt(num); i++) { | |
| if (num % i == 0) | |
| return false; | |
| } | |
| return true; | |
| } | |
| // Check all numbers for primality | |
| let sum = 0; | |
| for (let i = 2; i <= num; i++) { | |
| if (isPrime(i)) | |
| sum += i; | |
| } | |
| return sum; | |
| } |
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