ensureFields.js

/*
 * makes it easy to check an options object for required named params, e.g.
 *
 * export default function getBaseVolumeCurve(points, opts) {
 *  const {time, middleRange, lookbackPeriodDays, volPeriodDays} = ensureFields(opts);
 *  // ...
 * }
 *
 * if the key you're getting doesn't exist, it will throw an error
 */
export default function ensureFields(obj) {
  const handler = {
    get: (receiver, name) => {
      if (receiver[name] === undefined) {
        throw new Error(`Missing required argument ${name}`);
      }
      return receiver[name];
    }
  };

  return new Proxy(obj, handler);
}