# Check if a number is inside a given range with JavaScript

Given a number and a range, you can **check if the number falls within the specified range**. This can be useful when you need to validate user input or filter a list of numbers.

As the simplest solutions are often the best, we need only use **arithmetic comparison** to check if the number is in the specified range. If the second argument, `end`

, is not specified, the range is considered to be from `0`

to `start`

. If, however, the `start`

value is greater than the `end`

value, we can swap them to ensure that the range is valid.

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