Debounce and throttle functions from https://remysharp.com/2010/07/21/throttling-function-calls

throttle-debounce.js

function debounce(fn, delay) {
  var timer = null;
  return function () {
    var context = this, args = arguments;
    clearTimeout(timer);
    timer = setTimeout(function () {
      fn.apply(context, args);
    }, delay);
  };
}

function throttle(fn, threshhold, scope) {
  threshhold || (threshhold = 250);
  var last,
      deferTimer;
  return function () {
    var context = scope || this;

    var now = +new Date,
        args = arguments;
    if (last && now < last + threshhold) {
      // hold on to it
      clearTimeout(deferTimer);
      deferTimer = setTimeout(function () {
        last = now;
        fn.apply(context, args);
      }, threshhold);
    } else {
      last = now;
      fn.apply(context, args);
    }
  };
}

throttle-debounce.ts

function throttle<T, U>(fn: T extends Function ? T : Function, threshold = 1000, scope?: U) {
  let last: number
  let deferTimer: number
  return function(this: any) {
    const context = scope || this

    const now = +new Date()
    const args = arguments
    if (last && now < last + threshold) {
      // hold on to it
      clearTimeout(deferTimer)
      deferTimer = setTimeout(() => {
        last = now
        fn.apply(context, args)
      }, threshold)
    } else {
      last = now
      fn.apply(context, args)
    }
  }
}