turf-helpers

turf-helpers

feature

Wraps a GeoJSON Geometry in a GeoJSON Feature.

Parameters

• geometry Geometry input geometry
• properties Object properties

Examples

var geometry = {
     "type": "Point",
     "coordinates": [
       67.5,
       32.84267363195431
     ]
   }

var feature = turf.feature(geometry);

//=feature

Returns FeatureCollection a FeatureCollection of input features

point

Takes coordinates and properties (optional) and returns a new Point feature.

Parameters

• coordinates Array<number> longitude, latitude position (each in decimal degrees)
• properties [Object] an Object that is used as the Feature's properties

Examples

var pt1 = turf.point([-75.343, 39.984]);

//=pt1

Returns Feature<Point> a Point feature

polygon

Takes an array of LinearRings and optionally an Object with properties and returns a Polygon feature.

Parameters

• coordinates Array<Array<Array<number>>> an array of LinearRings
• properties [Object] a properties object

Examples

var polygon = turf.polygon([[
 [-2.275543, 53.464547],
 [-2.275543, 53.489271],
 [-2.215118, 53.489271],
 [-2.215118, 53.464547],
 [-2.275543, 53.464547]
]], { name: 'poly1', population: 400});

//=polygon

• Throws Error throw an error if a LinearRing of the polygon has too few positions or if a LinearRing of the Polygon does not have matching Positions at the beginning & end.

Returns Feature<Polygon> a Polygon feature

lineString

Creates a LineString based on a coordinate array. Properties can be added optionally.

Parameters

• coordinates Array<Array<number>> an array of Positions
• properties [Object] an Object of key-value pairs to add as properties

Examples

var linestring1 = turf.lineString([
[-21.964416, 64.148203],
[-21.956176, 64.141316],
[-21.93901, 64.135924],
[-21.927337, 64.136673]
]);
var linestring2 = turf.lineString([
[-21.929054, 64.127985],
[-21.912918, 64.134726],
[-21.916007, 64.141016],
	[-21.930084, 64.14446]
], {name: 'line 1', distance: 145});

//=linestring1

//=linestring2

• Throws Error if no coordinates are passed

Returns Feature<LineString> a LineString feature

featureCollection

Takes one or more Features and creates a FeatureCollection.

Parameters

• features Array<Feature> input features

Examples

var features = [
 turf.point([-75.343, 39.984], {name: 'Location A'}),
 turf.point([-75.833, 39.284], {name: 'Location B'}),
 turf.point([-75.534, 39.123], {name: 'Location C'})
];

var fc = turf.featureCollection(features);

//=fc

Returns FeatureCollection a FeatureCollection of input features

multiLineString

Creates a Feature<MultiLineString> based on a coordinate array. Properties can be added optionally.

Parameters

• coordinates Array<Array<Array<number>>> an array of LineStrings
• properties [Object] an Object of key-value pairs to add as properties

Examples

var multiLine = turf.multiLineString([[[0,0],[10,10]]]);

//=multiLine

• Throws Error if no coordinates are passed

Returns Feature<MultiLineString> a MultiLineString feature

multiPoint

Creates a Feature<MultiPoint> based on a coordinate array. Properties can be added optionally.

Parameters

• coordinates Array<Array<number>> an array of Positions
• properties [Object] an Object of key-value pairs to add as properties

Examples

var multiPt = turf.multiPoint([[0,0],[10,10]]);

//=multiPt

• Throws Error if no coordinates are passed

Returns Feature<MultiPoint> a MultiPoint feature

multiPolygon

Creates a Feature<MultiPolygon> based on a coordinate array. Properties can be added optionally.

Parameters

• coordinates Array<Array<Array<Array<number>>>> an array of Polygons
• properties [Object] an Object of key-value pairs to add as properties

Examples

var multiPoly = turf.multiPolygon([[[[0,0],[0,10],[10,10],[10,0],[0,0]]]);

//=multiPoly

• Throws Error if no coordinates are passed

Returns Feature<MultiPolygon> a multipolygon feature

geometryCollection

Creates a Feature<GeometryCollection> based on a coordinate array. Properties can be added optionally.

Parameters

• geometries Array<{Geometry}> an array of GeoJSON Geometries
• properties [Object] an Object of key-value pairs to add as properties

Examples

var pt = {
    "type": "Point",
      "coordinates": [100, 0]
    };
var line = {
    "type": "LineString",
    "coordinates": [ [101, 0], [102, 1] ]
  };
var collection = turf.geometrycollection([[0,0],[10,10]]);

//=collection

Returns Feature<GeometryCollection> a geometrycollection feature

This module is part of the Turfjs project, an open source module collection dedicated to geographic algorithms. It is maintained in the Turfjs/turf repository, where you can create PRs and issues.

Installation

Install this module individually:

$ npm install turf-helpers

Or install the Turf module that includes it as a function:

$ npm install turf