javascript binomial cooefficient

gistfile1.txt

function binomial(n, k) {
    if ((typeof n !== 'number') || (typeof k !== 'number')) 
    return false 
    let coeff = 1
    for (var x = n-k+1; x <= n; x++) coeff *= x
    for (x = 1; x <= k; x++) coeff /= x
    return coeff
}