node-geojson
Convert an array of objects with geometry to a GeoJSON feature collection.
Installation
npm install geojson
Getting Started
var GeoJSON = require('geojson');
Example Usage
The library has one method--parse
.
Take the example data below:
var data = [
{
name: 'Location A',
category: 'Store',
street: 'Market',
lat: 39.984,
lng: -75.343
},
{
name: 'Location B',
category: 'House',
street: 'Broad',
lat: 39.284,
lng: -75.833
},
{
name: 'Location C',
category: 'Office',
street: 'South'
lat: 39.123,
lng: -74.534
}
];
Convert it to GeoJSON:
GeoJSON.parse(data, {Point: ['lat', 'lng']});
{ "type": "FeatureCollection",
"features": [
{ "type": "Feature",
"geometry": {"type": "Point", "coordinates": [-75.343, 39.984]},
"properties": {
"name": "Location A",
"category": "Store"
}
},
{ "type": "Feature",
"geometry": {"type": "Point", "coordinates": [-75.833, 39.284]},
"properties": {
"name": "Location B",
"category": "House"
}
},
{ "type": "Feature",
"geometry": {"type": "Point", "coordinates": [ -75.534, 39.123]},
"properties": {
"name": "Location C",
"category": "Office"
}
}
]
}
Convert the example data to GeoJSON, and only include the name
attribute in properties
for each feature.
GeoJSON.parse(data, {Point: ['lat', 'lng'], include: ['name']});
{ "type": "FeatureCollection",
"features": [
{ "type": "Feature",
"geometry": {"type": "Point", "coordinates": [-75.343, 39.984]},
"properties": {
"name": "Location A"
}
},
...
{ "type": "Feature",
"geometry": {"type": "Point", "coordinates": [ -75.534, 39.123]},
"properties": {
"name": "Location C"
}
}
]
}
The parse
method can handle data with different geometry types
var data2 = [
{
x: 0.5,
y: 102.0,
prop0: 'value0'
},
{
line: [[102.0, 0.0], [103.0, 1.0], [104.0, 0.0], [105.0, 1.0]],
prop0: 'value0',
prop1: 0.0
},
{
polygon: [
[ [100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0] ]
],
prop0: 'value0',
prop1: {"this": "that"}
}
];
For each geometry type, specify which attribute contains the geometric data
GeoJSON.parse(data2, {'Point': ['x', 'y'], 'LineString': 'line', 'Polygon': 'polygon'});
{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"geometry": {
"type": "Point",
"coordinates": [102,0.5]
},
"properties": {
"prop0": "value0"
}
},
{
"type": "Feature",
"geometry": {
"type": "LineString",
"coordinates": [[102, 0], [103, 1], [104, 0],[105, 1]]
},
"properties": {
"prop0": "value0",
"prop1": 0
}
},
{
"type": "Feature",
"geometry": {
"type": "Polygon",
"coordinates": [[[100, 0], [101, 0], [101, 1], [100, 1], [100, 0]]]
},
"properties": {
"prop0": "value0",
"prop1": {
"this": "that"
}
}
}
]
}
Parameters
Depending on which makes more sense for your data, you either specify an array of attributes to include or exclude in properties
for each feature. If neither include
nor exclude
is set, all the attributes (besides the attributes containing the geometry data) will be added to properties
.
include
- Array of attributes to included in properties
objects. All other fields will be ignored.exclude
- Array of attributes to that shouldn't be included in properties
object. All other fields will be added (besides geometry fields)
The geometry parameters specify which attribute(s) contain(s) the geographic/geometric data. A geometry parameter must be specified for each type of geometry object that is present in your data. For example, if your data contains both points and polygons, you must specify both the Point
and Polygon
parameters. Note that geometry parameters must be in proper case. See the GeoJSON spec for details on each geometry type. The structure of the geometry parameter is:
ParameterName: 'attributeName'
Except for Point
, which can be specified with a field name or an array of field names, i.e:
data = [{
name: 'location',
x: 34,
y: 85
}];
GeoJSON.parse(data, {Point: ['lat', 'lng']});
data = [{
name: 'location',
coords: [y, x]
}];
GeoJSON.parse(data, {Point: 'coords'});
The valid geometry types are Point
, MultiPoint
, LineString
, MultiLineString
, Polygon
, and MultiPolygon
.