Generates primes up to a given number, using the Sieve of Eratosthenes.
Generate an array from 2
to the given number. Use Array.prototype.filter()
to filter out the values divisible by any number from 2
to the square root of the provided number.
代码片段
const primes = num => {
let arr = Array.from({ length: num - 1 }).map((x, i) => i + 2),
sqroot = Math.floor(Math.sqrt(num)),
numsTillSqroot = Array.from({ length: sqroot - 1 }).map((x, i) => i + 2);
numsTillSqroot.forEach(x => (arr = arr.filter(y => y % x !== 0 || y === x)));
return arr;
};
使用样例
primes(10); // [2,3,5,7]