Create a boolean array " prime [ 0 . . high ] " and initialize all entries it as true . A value in prime [ i ] will finally be false if i is Not a prime , else true .
var prime = Array . from ( { length : high + 1 } , ( _ , i ) => 0 ) ; var twin = false ; for ( i = 0 ; i < prime . length ; i ++ ) { prime [ i ] = true ; } prime [ 0 ] = prime [ 1 ] = false ;