franciskim/geojson-projector

Fast projector for immutable geojson

geojson-projector

Fast projector for immutable GeoJSON. It can project any branch of GeoJSON object.

geojson-projector can produce the cacheing of projected values which is a good point while one is using immutable data flow.

Instalation

npm install --save geojson-projector

Usage

import GeojsonProjector from 'gojson-projector';
let project = GeojsonProjector('EPSG:4326', 'EPSG:3857');

// use cases
let coordinates = project([-122.416667, 37.783333]);
let geometry = project({
    "type": "Point",
    "coordinates": [-122.416667, 37.783333]
});
let feature = project({
    "type": "Feature",
    "geometry": {
        "type": "LineString",
        "coordinates": [
            [-122.416667, 37.783333],
            [4.900000, 52.366667]
        ]
    }

});
let geojson = project({
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "geometry": {
                "type": "Point",
                "coordinates": [-122.416667, 37.783333]
            }
        },
        {
            "type": "Feature",
            "geometry": {
                "type": "LineString",
                "coordinates": [
                    [-122.416667, 37.783333],
                    [4.900000, 52.366667]
                ]
            }

        }
    ]
})

Immutable input GeoJSON mode

In case of immutable input GeoJSON mode projector produce cacheing of output results based upon input source instance. Immutable input GeoJSON mode is used by default.

import {isEqual, clone} from 'lodash';
import {GeojsonProjector} from 'gojson-projector';

let project = GeojsonProjector({
    from: 'EPSG:4326',
    to: 'EPSG:3857',
    immutable: true
});
let geometry = project({
    "type": "Point",
    "coordinates": [-122.416667, 37.783333]
});
let projection1 = project(geometry);
let projection2 = project(geometry);
let projectionOfClone = project(clone(geometry));

console.log(projection1 === projection2); // true
console.log(projection1 !== projectionOfClone); // true
console.log(isEqual(projection1, projectionOfClone)); // true

Mutable input GeoJSON mode

In case of mutable input GeoJSON mode projector produce a new calculation per each project call.

import {isEqual, clone} from 'lodash';
import {GeojsonProjector} from 'gojson-projector';

let project = GeojsonProjector({
    from: 'EPSG:4326',
    to: 'EPSG:3857',
    immutable: false
});
let geometry = project({
    "type": "Point",
    "coordinates": [-122.416667, 37.783333]
});
let projection1 = project(geometry);
let projection2 = project(geometry);

console.log(projection1 !== projection2); // true
console.log(isEqual(projection1, projectionOfClone)); // true