periodicjs.ext.reactapp/utilities/reloader.js

react based admin.

'use strict';
const Promisie = require('promisie');
const fs = Promisie.promisifyAll(require('fs-extra'));
const path = require('path');
const CACHE = require.cache;
const WATCHED = new Map();

var debounce = function (fn) {
  let timeout;
  return function () {
    if (!timeout) timeout = setTimeout(fn, 1500);
    else {
      clearTimeout(timeout);
      timeout = setTimeout(fn, 1500);
    }
  };
};

var flushCached = function (filepath, fn, isModule) {
  return debounce(() => {
    if (isModule) delete CACHE[ filepath ];
    if (typeof fn === 'function') fn();
    console.log('::HOT RELOAD::', { filepath, });
  });
};

var watcher = function (filepath, onChange, periodic) {
  let isModule = (path.extname(filepath) === '.js');
  if (!WATCHED.has(filepath)) {
    let listener;
    if (typeof onChange !== 'function') listener = flushCached(filepath, null, isModule);
    else listener = flushCached(filepath, onChange, isModule);
    fs.watch(filepath, 'utf8', listener);
    WATCHED.set(filepath, true);
  }
  if (isModule) {
    let requiredFile = require(filepath);
    requiredFile = (typeof requiredFile === 'function')
      ? requiredFile(periodic)
      : requiredFile;
    return Promisie.resolve(requiredFile);
  } else {
    return fs.readJsonAsync(filepath);
  }
};

module.exports = watcher;