Throttle

throttle.js

/**
 * Creates and returns a new, throttled version of the passed function,
 * that, when invoked repeatedly, will only actually call the original
 * function at most once per every wait milliseconds.
 *
 * @param {function} func
 * @param {number} threshold
 * @param {object} [scope] custom this
 * @returns {function} throttled function
 */
export function throttle(func, threshold, scope) {
  const FUNC_ERROR_TEXT = 'First parameter must be a function.';
  let last;
  let deferTimer;

  if (typeof func !== 'function') {
    throw new TypeError(FUNC_ERROR_TEXT);
  }

  return function throttled(...args) {
    const context = this || scope;
    const now = +new Date();

    if (last && now < last + threshold) {
      clearTimeout(deferTimer);

      deferTimer = setTimeout(() => {
        last = now;
        func.apply(context, args);
      }, threshold);
    } else {
      last = now;
      func.apply(context, args);
    }
  };
}