Throttle will make sure a function is only called once within the given amount of time

throttle.ts

/**
 * Throttle will make sure a function is only called once within the given amount of time
 * must use function to keep `this` context
 */
function throttle(fn: Function, threshold: number = 250) {
  // check function
  if (typeof fn !== 'function') {
    throw new TypeError('You must provide a function as the first argument for throttle.');
  }

  // check threshold
  if (typeof threshold !== 'number') {
    throw new TypeError('You must provide a number as the second argument for throttle.');
  }

  let lastEventTimestamp: number | null = null;

  return (...args: any) => {
    const now = Date.now();
    if (lastEventTimestamp === null || now - lastEventTimestamp >= threshold) {
      lastEventTimestamp = now;
      fn.apply(this, args);
    }
  };
};