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You can declare Array with running numbers up by using [...Array(n).keys]. Then if you want it start from 1, you just increase array size then slice it of.
const isPerfect = n => [...Array(n).keys()].slice(1).filter(e => !(n % e)).reduce((a, b) => a + b) === n- const isPerfect = n =>
Array(n - 1).fill(1).map((e, i) => e + i).filter(e => n % e === 0).reduce((a, b) => a + b) === n- [...Array(n).keys()].slice(1).filter(e => !(n % e)).reduce((a, b) => a + b) === n