Calculate combinations count in Javascript (ES5)

combinations.js

function combinationsCount(m, n) {
  if (m < n) {
    return 0;
  } else if (m === n || n === 0) {
    return 1;
  } else {
    var c = 1, i;
    for (i = n + 1; i <= m; i ++) {
      c *= i;
    }
    for (i = 2; i <= m - n; i ++) {
      c /= i;
    }
    return c;
  }
}