[Javascript] Using Generator to create a number generate with condition

const generateTimeMs = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min

/**
 * A generator which can generate numbers based on settings
 *
 * @param {number} min - min timer value, unit ms
 * @param {number} max - max timer value, unit ms
 * @param {number} minDiff - ensure that max - min > minDiff always true
 * @returns
 */
function* RCTimer(min, max, minDiff) {
    let invalidate = min + minDiff > max
    if (invalidate) {
        return new Error(`min value + minDiff value should less than max value`)
    }
    while (!invalidate) {
        const firstTimer = generateTimeMs(min + minDiff, max)
        yield firstTimer

        const secondTimer = generateTimeMs(min, firstTimer - minDiff)
        yield secondTimer
    }
}

const gen = RCTimer(1000, 4000, 2000)
let count = 0
while (count < 3) {
  count++
  console.log(`Round ${count}: `)
  const firstTimer = gen.next()
  console.log(`firstTimer: ${JSON.stringify(firstTimer)}`)
  const secondTimer = gen.next()
  console.log(`secondTimer: ${JSON.stringify(secondTimer)}`)
}

/**
 * Round 1: 
firstTimer: {"value":3365,"done":false}
secondTimer: {"value":1347,"done":false}
Round 2: 
firstTimer: {"value":3181,"done":false}
secondTimer: {"value":1075,"done":false}
Round 3: 
firstTimer: {"value":3682,"done":false}
secondTimer: {"value":1672,"done":false}
 */