mobx-utils/lib/now.js

Utility functions and common patterns for MobX

import { _isComputingDerivation } from "mobx";
import { fromResource } from "./from-resource";
var tickers = {};
/**
 * Disposes of all the internal Observables created by invocations of `now()`.
 *
 * The use case for this is to ensure that unit tests can run independent of each other.
 * You should not call this in regular application code.
 *
 * @example
 * afterEach(() => {
 *     utils.resetNowInternalState()
 * })
 */
export function resetNowInternalState() {
    for (var _i = 0, _a = Object.getOwnPropertyNames(tickers); _i < _a.length; _i++) {
        var key = _a[_i];
        tickers[key].dispose();
        delete tickers[key];
    }
}
/**
 * Returns the current date time as epoch number.
 * The date time is read from an observable which is updated automatically after the given interval.
 * So basically it treats time as an observable.
 *
 * The function takes an interval as parameter, which indicates how often `now()` will return a new value.
 * If no interval is given, it will update each second. If "frame" is specified, it will update each time a
 * `requestAnimationFrame` is available.
 *
 * Multiple clocks with the same interval will automatically be synchronized.
 *
 * Countdown example: https://jsfiddle.net/mweststrate/na0qdmkw/
 *
 * @example
 *
 * const start = Date.now()
 *
 * autorun(() => {
 *   console.log("Seconds elapsed: ", (mobxUtils.now() - start) / 1000)
 * })
 *
 *
 * @export
 * @param {(number | "frame")} [interval=1000] interval in milliseconds about how often the interval should update
 * @returns
 */
export function now(interval) {
    if (interval === void 0) { interval = 1000; }
    if (!_isComputingDerivation()) {
        // See #40
        return Date.now();
    }
    if (!tickers[interval]) {
        if (typeof interval === "number")
            tickers[interval] = createIntervalTicker(interval);
        else
            tickers[interval] = createAnimationFrameTicker();
    }
    return tickers[interval].current();
}
function createIntervalTicker(interval) {
    var subscriptionHandle;
    return fromResource(function (sink) {
        sink(Date.now());
        subscriptionHandle = setInterval(function () { return sink(Date.now()); }, interval);
    }, function () {
        clearInterval(subscriptionHandle);
    }, Date.now());
}
function createAnimationFrameTicker() {
    var frameBasedTicker = fromResource(function (sink) {
        sink(Date.now());
        function scheduleTick() {
            window.requestAnimationFrame(function () {
                sink(Date.now());
                if (frameBasedTicker.isAlive())
                    scheduleTick();
            });
        }
        scheduleTick();
    }, function () { }, Date.now());
    return frameBasedTicker;
}