Frontend: Throttle (Leading Edge, Fixed Window)

```js

function throttle(fn, interval) {

let lastFire = -Infinity;

return function (...args) {

const now = Date.now();

if (now - lastFire >= interval) {

lastFire = now;

fn.apply(this, args);

}

// else drop

};

}

```

Variants worth knowing:

- Trailing edge: ignore the first call, fire the last call after `interval` of silence (this is debounce, not throttle).

- Leading + trailing: fire immediately AND fire once at the end of the window if any calls were dropped (the lodash default).

- Sliding window vs fixed window: the implementation above is "fixed window from last fire". A sliding-window throttle would maintain a queue.

Throttle vs debounce - the canonical question:

- Throttle: "max N calls per second". Fires steadily during a continuous stream. Good for scroll, mousemove, window-resize - things you want updated periodically.

- Debounce: "wait for silence". Only fires when the input stops. Good for search-as-you-type, autosave, expensive validations.

`requestAnimationFrame` as a throttle for animations: `requestAnimationFrame(fn)` runs once per repaint (~60fps), naturally throttling visual updates. Better than `setTimeout(fn, 16)` because it pauses on backgrounded tabs.