Throttle a channel in js-csp

throttle.js

// https://github.com/jlongster/js-csp
// Throttle ported from:
// https://gist.github.com/swannodette/5886048

var csp = require('js-csp');
var chan = csp.chan;
var go = csp.go;
var put = csp.put;
var take = csp.take;
var timeout = csp.timeout;

function listen(el, type, ch) {
  ch = ch || chan();
  el.addEventListener(type, function(e) {
    csp.putAsync(ch, e);
  });
  return ch;
}

function throttle(inCh, ms) {
  var outCh = chan();
  go(function*() {
    while(true) {
      yield put(outCh, yield take(inCh));
      yield take(timeout(ms));
    }
  });
  return outCh;
}

go(function*() {
  var el = document.getElementById('location');
  // Important that the source channel `ch` be a sliding buffer of size 1
  var ch = listen(el, 'mousemove', chan(csp.buffers.sliding(1)));
  var throttledCh = throttle(ch, 500);
  while(true) {
    var e = yield take(throttledCh);
    el.innerHTML = ((e.layerX || e.clientX) + ', ' +
                    (e.layerY || e.clientY));
  }
});