Implement a throttle function which accepts a callback function and a wait duration. Calling throttle() returns a function which throttled invocations of the callback function following the described behaviour.

throttle.ts

/**
 * Throttling is a technique used to control how many times we allow a function to be executed over time.
 * When a JavaScript function is said to be throttled with a wait time of X milliseconds, it can only be invoked at most once every X milliseconds.
 * The callback is invoked immediately and cannot be invoked again for the rest of the wait duration.
 */
type ThrottleFunction<T extends any[]> = (...args: T) => any;

export default function throttle<T extends any[]>(
  func: ThrottleFunction<T>,
  wait: number
): ThrottleFunction<T> {
  let timer: ReturnType<typeof setTimeout> | null = null;
  return function (this: any, ...args: T) {
    if (!timer) {
      func.apply(this, args);
      timer = setTimeout(() => {
        clearTimeout(timer!);
        timer = null;
      }, wait);
    }
  };
}

let i = 0;
function increment() {
  i++;
}
const throttledIncrement = throttle(increment, 100);

throttledIncrement();
console.log(i); //1
setTimeout(() => {
  throttledIncrement();
  console.log(i); //1
}, 50);
setTimeout(() => {
  throttledIncrement();
  console.log(i); //2
}, 101);