10-modulmetoden i Javascript för att validera svenska personnummer

10-modulmetoden.js

function getCheckSum(ch) {
	let ps = ch.slice(0, -1).split('').reverse()

	let sums = ps.map((s, i) => {
		let m = (i % 2 == 0) ? 2 : 1;
		let rem = (parseInt(s) * m).toString().split('')
		return rem.reduce((d,a) => Number(d) + Number(a), 0)
	})
	
	let res = sums.reduce((d,a) => Number(d) + Number(a), 0)
	return (Math.ceil(res / 10) * 10 - res)
}

function isValidIdNumber(ch) {
	if (ch.length !== 10) throw new Error("Length must be exactly 10")
	return ch.slice(-1) == getCheckSum(ch.slice(0, -1))
}