How do I find the latitude and longitude range shown by my leaflet map?

I am using javascript fetch in the browser to pull geographical datapoints from my API and populate them to a Leaflet.JS map.

At the moment my API is returning all the markers globally in response to every request, which is fine for testing but will obviously become inefficient once there are many markers.

I want to limit the scope of the request by location such that it just returns the relevant markers for the user (ie those which are shown on the map area they are currently viewing). This is fine on the backend, but I can't find out how to get the lat/lon coordinate range that is shown on the map. The map should request new data when it is panned or zoomed.

Ideally there would be functionality to load a wider range of data than the shown area (ex 3x) to allow for some panning/zooming without requesting more data from the server, and only make another request then the pan/zoom expands beyond that area.

This seems like a common use case but I couldn't find any examples.

I could find numerous examples for getting lat and lon from a click event, but I want to know the top left and bottom right lat/lon, and ideally find some useful tips for how to request this data in a sensible way.

Answer from my comment:
You can use getBounds method which will return LatLngBounds which contain coordinates of both corners you are looking for.

Thank you to @zerdox for pointing me in the right direction. "Bounds" is the term I was looking for.

Posting my working code:

// Allow the map to update as it is panned
let last_map_update = 0
const throttle_ms = 500
map.on("move", function () {
	if ((Date.now() - last_map_update) > throttle_ms) {
		update_map_data()
		last_map_update = Date.now()
	}
});

function update_map_data() {
	let map_bounds = map.getBounds();
	let northEast = map_bounds['_northEast']
	let southWest = map_bounds['_southWest']

	fetch(api_url + '/api/map?'+ new URLSearchParams({
		'northEastLat': northEast['lat'],
		'northEastLon': northEast['lng'],
		'southWestLat': southWest['lat'],
		'southWestLon': southWest['lng'],
	}), {
		method: 'GET',
	})
		.then(response => response.json())
		.then(data => {
			units_to_show_on_map = data.units
			show_map_markers()
		})
		.catch(rejected => {
			console.log(rejected)
		})
}