throttle and debounce

[gt3]

Controlling streaming data with channels is a powerful concept. Yet too much boilerplate goes into implementing functions like throttle and debounce.

I'm proposing that we add few helpers to provide out of the box standard functionality.

let { go, chan, poll, put, putAsync, timeout, NO_VALUE, CLOSED, buffers } = csp

function* readThenCall(cb, inch, delay = 0) {
  let msg = yield inch,
    cancelled
  let cancel = () => {
    cancelled = true
  }
  while (msg !== CLOSED) {
    cb(msg, cancel)
    if (cancelled) break
    if (delay > 0) yield timeout(delay)
    msg = yield inch
  }
}

function* readThenPut(outch, inch, delay = 0) {
  let msg = yield inch,
    cancelled
  while (msg !== CLOSED) {
    cancelled = !(yield put(outch, msg))
    if (cancelled) break
    if (delay > 0) yield timeout(delay)
    msg = yield inch
  }
}

function* readThenPutThrottled(delay, inch, outch) {
  let msg = poll(inch),
    cancelled
  if (msg !== NO_VALUE) cancelled = !(yield put(outch, msg))
  if (!cancelled) go(readThenPut, [outch, inch, delay])
}

// export
function throttle(cb, delay, inch, outch = chan(1)) {
  go(readThenCall, [cb, outch])
  go(readThenPutThrottled, [delay, inch, outch])
  return outch
}

---

• demo
• gist

I can create a PR once we agree on the requirements.

cc: @hung-phan @ubolonton
related to #133

[frankandrobot]

So note that my example already has a working debounce. The only thing missing is that it needs to stop when the input channel is closed.

[gt3]

Totally your code inspired me to open this issue. I just refactored it a bit. I wanted to show how simple it is to go from throttle to debounce using Channels as the interface. Thanks again for making that example.