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