Check if the given number falls within the given range

Use arithmetic comparison to check if the given number is in the specified range. If the second argument, end, is not specified, the range is considered to be from 0 to start.

const inRange = (n, start, end = null) => {
  if (end && start > end) [end, start] = [start, end];
  return end == null ? n >= 0 && n < start : n >= start && n < end;
};

// Examples
inRange(3, 2, 5); // true
inRange(3, 4); // true
inRange(2, 3, 5); // false
inRange(3, 2); // false

Source

https://www.30secondsofcode.org/js/s/in-range