Rate-limiter/debouncer module for JavaScript. See https://code.hnldesign.nl/demo/hnl.debounce.html

debouncer.mjs

/**
 *
 * debounceThis ES6 module v1.2 (03-2023)
 * Debounces/rate-limits the provided function (callback)
 *
 * Example usage:
 *
 * import {debounceThis} from "debouncer.mjs";
 *
 * window.addEventListener('scroll', debounceThis((e)=> {
 *    //function that will be debounced/rate-limited
 *    updateScrollPos('after-scroll');
 * }, {
 *    //optional parameters, see _defaults below
 *    execStart: false,
 *    execWhile: false,
 *    execDone: true
 * }))
 *
 * See demo at https://code.hnldesign.nl/demo/hnl.debounce.html
 */

const _defaults = {
  threshold: 150, //time to wait
  execStart: false, //execute callback once immediately?
  execWhile: false, //execute callback at each threshold interval while debouncing function is being called?
  execDone: true,   //execute callback once debouncing function stops being called and threshold passed?
}

export function debounceThis(cb, opts) {

  //get/set options
  opts = Object.assign({
    timer: 0,
    whileTimer: 0,
    busy: false,
  }, _defaults, opts);

  return function (...args) {
    clearTimeout(opts.timer);

    if (!opts.busy && opts.execStart) {
      cb.apply(this, args);
      opts.busy = true;
    }

    if (opts.execWhile && !opts.whileTimer) {
      opts.whileTimer = setTimeout(() => {
        cb.apply(this, args);
        opts.whileTimer = false;
      }, opts.threshold);
    }

    opts.timer = setTimeout(() => {
      opts.busy = false;
      if (opts.execDone) cb.apply(this, args);
      clearInterval(opts.whileTimer);
    }, opts.threshold);
  }
}