Alternate Primes till N | Javascript program to print all primes smaller than or equal to n using Sieve of Eratosthenes ; Create a boolean array " prime [ 0 . . n ] " and initialize all entries it as true . A value in prime [ i ] will finally be false if i is Not a prime , else true . ; If prime [ p ] is not changed , then it is a prime ; Update all multiples of p ; Print all prime numbers ; for next prime to get printed ; Driver Code
function SieveOfEratosthenes ( n ) { let prime = new Array ( n + 1 ) ; for ( let i = 0 ; i < prime . length ; i ++ ) prime [ i ] = true ; for ( let p = 2 ; p * p <= n ; p ++ ) { if ( prime [ p ] == true ) { for ( let i = p * 2 ; i <= n ; i += p ) prime [ i ] = false ; } } let flag = true ; for ( let p = 2 ; p <= n ; p ++ ) { if ( prime [ p ] ) { if ( flag ) { document . write ( p + " " ) ; flag = false ; } else { flag = true ; } } } } let n = 15 ; document . write ( " " + " " + " " + n + " " ) ; SieveOfEratosthenes ( n ) ;