Site settings and fires fromNow Reactive

imports/ui/components/Chronos/Chronos.js

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+// Adapted from: https://github.com/remcoder/chronos (MIT License)
+
+import { Meteor } from 'meteor/meteor';
+import { Tracker } from 'meteor/tracker';
+import { ReactiveVar } from 'meteor/reactive-var';
+import moment from 'moment';
+
+const _timers = {};
+
+function Timer(interval) {
+  this.interval = interval || 1000;
+  this.time = new ReactiveVar(0);
+}
+
+Timer.prototype.start = function () {
+  if (this._timer) throw new Error('Trying to start Chronos.Timer but it is already running.');
+  this.time.set(new Date());
+
+
+  this._timer = setInterval(Meteor.bindEnvironment(() => {
+    // console.log('tick', this._timer);
+    this.time.set(new Date());
+  }), this.interval);
+};
+
+Timer.prototype.stop = function () {
+  // console.log('stopping timer');
+  clearInterval(this._timer);
+  this._timer = null;
+};
+
+function _update(interval) {
+  // get current reactive context
+  const comp = Tracker.currentComputation;
+  if (!comp) { return; } // no nothing when used outside a reactive context
+
+  // only create one timer per reactive context to prevent stacking of timers
+  const cid = comp && comp._id;
+  if (!_timers[cid]) {
+    const timer = new Timer(interval);
+    _timers[cid] = timer;
+
+    // add destroy method that stops the timer and removes itself from the list
+    timer.destroy = function () {
+      timer.stop();
+      delete _timers[cid];
+    };
+
+    timer.start();
+  }
+
+  // make sure to stop and delete the attached timer when the computation is stopped
+  comp.onInvalidate(() => {
+    // console.log('onInvalidated',comp);
+    if (comp.stopped && _timers[cid]) {
+      // console.log('computation stopped');
+      _timers[cid].destroy();
+    }
+  });
+
+  _timers[cid].time.dep.depend(comp); // make dependent on time
+
+  // console.log(_timers);
+  return _timers[cid];
+}
+
+// reactive version of moment()
+// please install moment separately
+// example usage: Chronos.moment(someTimestamp).format('ss');
+function _moment(/* arguments */) {
+  if (!moment) throw new Error('moment not found. Please install it first');
+
+  _update();
+  return moment(...arguments);
+}
+
+// reactive version of new Date() get the current date/time
+function _date(interval) {
+  _update(interval);
+  return new Date();
+}
+
+// reactive version of Date.now(). get the current # of milliseconds since the start of the epoch
+function _now(interval) {
+  _update(interval);
+  return Date.now();
+}
+
+// export global
+const Chronos = {
+
+  // a simple reactive timer
+  // usage: var timer = new Timer();
+  // get current time: timer.time.get();
+  Timer,
+
+  // handy util func for making reactive contexts live updating in time
+  // usage: simply call Chronos.update() in your helper to make it execute
+  // every interval
+  update: _update,
+
+  // reactive version of new Date() get the current date/time
+  date: _date,
+
+  // reactive version of Date.now(). get the current # of milliseconds since the start of the epoch
+  now: _now,
+
+  // reactive version of moment()
+  // please install moment separately
+  // example usage: Chronos.moment(someTimestamp).format('ss');
+  moment: _moment,
+
+  // for debugging and testing
+  _timers,
+
+  // deprecated. but kept for backwards compatibility
+  liveUpdate: _update,
+  currentTime: _date,
+  liveMoment: _moment
+};
+
+export default Chronos;