conditions.js

function inRange(min, max, value) {
    return (min == null || min <= value) &&
           (max == null || max >= value)
}

// evalutation of inRange(1, 2, 1.5)
(1 == null || 1 <= 1) && (2 == null || 2 >= 1)
(false || true) && (false || true)
true && true
true

// evaluation of inRange(1, null, 1.5)
(1 == null || 1 <= 1.5) && (null == null || null >= 1.5)
(false || true) && (true || false)
true && true
true