What is Throttling? How to implement it in JS?

const expensive = () => {  console.log('Expensive function');}

const throttle = (fn, delay) => {  let wait = false;  const throttledFunction = () => {    if (wait) return; // If wait is true, it means the timer// is still running and the function shouldn't be executed    fn();    wait = true;    setTimeout(() => {      wait = false;    }, delay);  return throttledFunction;}const inExpensive = throttle(expensive, 1000);

const throttle = (fn, delay) => {  let wait = false;  let storedArgs = null;  const throttledFunction = (...args) => {    if (wait) {      storedArgs = args;      return    }    fn(...storedArgs);    wait = true;    setTimeout(() => {      wait = false;    }, delay);  }  return throttledFunction;}