calculateZoom.js

/**
 * https://stackoverflow.com/a/6055653/961045
 * 
 * this.map = instance of NguiMapComponent ( https://github.com/ng2-ui/map)
 * this.mapOptions = options to be passed in to map component ( https://developers.google.com/maps/documentation/javascript/reference#MapOptions )
 * this.sitesWithLocations = objects with a location property of type { coordinates: [long, lat] }
 */
calculateZoom() {
    if (this.map && this.map.el) {
        const GLOBE_WIDTH = 256; // a constant in Google's map projection
        const longs = this.sitesWithLocations.map(site => site.location.coordinates[0]);
        const west = Math.min(...longs);
        const east = Math.max(...longs);
        let angle = east - west;
        if (angle < 0) {
            angle += 360;
        }
        const mapWidth = this.map.el.offsetWidth;
        let zoom = Math.round(Math.log(mapWidth * 360 / angle / GLOBE_WIDTH) / Math.LN2) - 1;
        if (zoom === Infinity) { // when there are no sites with locations
            zoom = SitesMapComponent.DEFAULT_ZOOM; // a static value set to 10 in the JS class this was pulled from
        }
        this.mapOptions.zoom = zoom;
    }
}