driftless/src/driftless.js

Driftless setInterval and setTimeout replacement for Node and the browser

import present from 'present';

export const DEFAULT_THRESHOLD_MS = 1;
export const DEFAULT_AGGRESSION = 1.1;
export const DEFAULT_NOW_FN = (...args) => present(...args);
export const DEFAULT_SET_TIMEOUT = (...args) => setTimeout(...args);
export const DEFAULT_CLEAR_TIMEOUT = (...args) => clearTimeout(...args);

const timerHandles = {};
let nextId = 0;

function tryDriftless(id, opts) {
  const {
    atMs,
    fn,
    thresholdMs = DEFAULT_THRESHOLD_MS,
    aggression = DEFAULT_AGGRESSION,
    customNow = DEFAULT_NOW_FN,
    customSetTimeout = DEFAULT_SET_TIMEOUT,
  } = opts;
  const delayMs = atMs - customNow();

  const handle = delayMs > thresholdMs
    ? (
      customSetTimeout(() => {
        tryDriftless.apply(this, arguments); // eslint-disable-line prefer-rest-params
      }, delayMs / aggression)
    )
    : (
      customSetTimeout(() => {
        // Call the function using setTimeout to ensure asynchrony
        fn();
      }, 0)
    );

  timerHandles[id] = handle;
}

export function setDriftless(...args) {
  return setDriftless.setDriftlessSpyable(...args);
}

// Separate function for testing
setDriftless.setDriftlessSpyable = (opts) => {
  const id = nextId;
  nextId += 1;
  tryDriftless(id, opts);
  return id;
};

export function clearDriftless(id, opts = {}) {
  const {
    customClearTimeout = DEFAULT_CLEAR_TIMEOUT,
  } = opts;
  customClearTimeout(timerHandles[id]);
}

function castToFn(fn) {
  return typeof fn === 'function'
    ? fn
    : new Function(fn); // eslint-disable-line no-new-func
}

export function setDriftlessTimeout(fn, delayMs, ...params) {
  const callFn = castToFn(fn);
  return setDriftless({
    atMs: DEFAULT_NOW_FN() + delayMs,
    fn(...args) {
      return callFn.call(this, ...args, ...params);
    },
  });
}

export function setDriftlessInterval(fn, delayMs, ...params) {
  const callFn = castToFn(fn);
  let id;
  const opts = {
    atMs: DEFAULT_NOW_FN() + delayMs,
    fn(...args) {
      opts.atMs += delayMs;
      tryDriftless(id, opts);
      return callFn.call(this, ...args, ...params);
    },
  };
  id = setDriftless(opts);
  return id;
}