I'd like to have a slightly altered behavior for lodash's throttle function

@Jonas Wilms, thank you for your answer. I didn't really like the use of Date and I found that writing a throttle function is actually quite trivial. At first I didn't know that, because lodash's throttle function is based on their debounce function and their debounce function looks a bit complicated to me.

Anyhow, I ended up writing this function, which seems to do the job.

export function throttle(fn, ...delays) {
  let t1, t2, activeDelay = 0

  return function() {
    if (t2) {
      clearTimeout(t2)
      t2 = undefined
    }

    if (t1) {
      return
    }

    t1 = setTimeout(() => {
      fn(...arguments)
      t1 = undefined

      // Increment the active delay each time
      // and then stick with the last one.
      activeDelay = Math.min(++activeDelay, delays.length - 1)

      // Set a 2nd `Timeout` that resets the
      // active delay back to the first one.
      t2 = setTimeout(() => {
        activeDelay = 0
        t2 = undefined
      }, delays[activeDelay])

    }, delays[activeDelay])
  }
}

You could maintain a date containing the time the last call was scheduled for:

 function throttle(fn, initial, cooldown) {
   let last = 0;
   return function throttled(...args) {
    setTimeout(fn, Math.max(0, cooldown + last - (last = Date.now())) || initial, ...args);
   }
 }