Q:

STRING parameter of type 'GeoJsonObject'

Leaf let documentation said :
import * as L from 'leaflet';

https://raw.githubusercontent.com/alanent/france-geojson/master/regions/pays-de-la-loire/departements-pays-de-la-loire.geojson
The GeoJSON layer
GeoJSON objects are added to the map through a GeoJSON layer. To create it and add it to a map, we can use the following code:
ngOnInit{
L.GeoJSON(geojsonFeature).addTo(myfrugalmap);
}

The geojson is drawn but i receive an error :

ERROR in src/app/geo/geo.component.ts(335,11): error TS2345: Argument
 of type '{ "type": string; "features": ({ "type": string; "geometry":
{ "type": string; "coordinates": num...' is not assignable to
 parameter of type 'GeoJsonObject'.   Property 'type' is missing in
type '{ "type": string; "features": ({ "type": string; "geometry": {
"type": string; "coordinates": num...'.

Can i ignore this error ?

A:

amenity and popupContent does not exist in type declaration
should be: 
import * as L from 'leaflet';

var geojsonFeature = {
    "type": "Feature",
    "properties": {
       "name": "Location B",
       "category": "House"
    },
    "geometry": {
        "type": "Point",
        "coordinates": [-104.99404, 39.75621]
    }
};

ngOnInit{
    L.geoJSON(geojsonFeature).addTo(map); // or L.geoJSON([geojsonFeature]).addTo(map);
}

See here docs https://www.npmjs.com/package/geojson#readme

