index.js

module.exports = normalize;

var types = {
    Point: 'geometry',
    MultiPoint: 'geometry',
    LineString: 'geometry',
    MultiLineString: 'geometry',
    Polygon: 'geometry',
    MultiPolygon: 'geometry',
    GeometryCollection: 'geometry',
    Feature: 'feature',
    FeatureCollection: 'featurecollection'
};

/**
 * Normalize a GeoJSON feature into a FeatureCollection.
 *
 * @param {object} gj geojson data
 * @returns {object} normalized geojson data
 */
function normalize(gj) {
    if (!gj || !gj.type) return null;
    var type = types[gj.type];
    if (!type) return null;

    if (type === 'geometry') {
        return {
            type: 'FeatureCollection',
            features: [{
                type: 'Feature',
                properties: {},
                geometry: gj
            }]
        };
    } else if (type === 'feature') {
        return {
            type: 'FeatureCollection',
            features: [gj]
        };
    } else if (type === 'featurecollection') {
        return gj;
    }
}