calculate the extent of a geoJSON geometry

dataextent.js

/**
 * @data : Object object parsed from a geoJSON file.
 * @options: used internally as this function calls itself recursively.
 **/
	const dataExtent = (data, {depth=0, inCoordinates=false, extent}={}) => {
		if (!extent) {
			extent = [[Infinity, Infinity], [-Infinity, -Infinity]];
		}
		
		if (Array.isArray(data)) {
			if (
				inCoordinates &&
				data.length > 1 &&
				typeof data[0] === 'number' &&
				typeof data[1] === 'number'
				) {
					extent[0][0] = Math.min(extent[0][0], data[0]);
					extent[1][0] = Math.max(extent[1][0], data[0]);
					extent[0][1] = Math.min(extent[0][1], data[1]);
					extent[1][1] = Math.max(extent[1][1], data[1]);
			}
			else {
				for (let chunk of data) {
					extent = dataExtent(
						chunk, {depth: depth + 1, inCoordinates, extent});
				}
			}
		}
		else if (data && typeof data === 'object') {
			for (let [key, chunk] of Object.entries(data)) {
				if (key === 'coordinates') {
					inCoordinates = true;
				}
				extent = dataExtent(
					chunk, {depth: depth + 1, inCoordinates, extent});
			}
		}
		
		if (depth === 0) {
			extent = [
				extent[0],
				[
					extent[1][0],
					extent[0][1],
				],
				extent[1],
				[
					extent[0][0],
					extent[1][1],
				],
			];
		}
		return extent;
	}
	
//usage:
//this function takes as argument 
//an object resulting from parsing
//the content of a geoJSON file.
//the returned value is an array of
//four points surrounding all the points
//in the input file.
//this may be used 
//in leaflet as a bounding box
//and in openlayers as the extent of a map.