geojson.js
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
, which takes an array of objects with geometry data as the first parameter, and an object consisting of settings for the second parameter.
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. Consider the following sample data:
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"
}
}
}
]
}
You can also specify default settings if you will be parsing mutliple datasets with similiar attributes.
var data1 = [{
name: 'Location A',
street: 'Market',
x: 34,
y: -75
}];
var data2 = [{
name: 'Location B',
date: '11/23/2012',
x: 54,
y: -98
}];
GeoJSON.defaults = {Point: ['x', 'y'], include: ['name']};
GeoJSON.parse(data1);
{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"geometry": {
"type": "Point",
"coordinates": [-75, 34]
},
"properties": {
"name": "Location A"
}
}
]
}
GeoJSON.parse(data2);
{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"geometry": {
"type": "Point",
"coordinates": [-98, 54]
},
"properties": {
"name": "Location B"
}
}
]
}
Parameters
Depending on which makes more sense for the data that is being parsed, 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 feature properties
.
include
- Array of attributes to include in properties
for each feature. All other fields will be ignored.exclude
- Array of attributes that shouldn't be included in feature properties
. All other attributes will be added (besides geometry attributes)
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 the data that is being parsed. For example, if the data contains both points and polygons, 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: [85, 34]
}];
GeoJSON.parse(data, {Point: 'coords'});
The valid geometry types are Point
, MultiPoint
, LineString
, MultiLineString
, Polygon
, and MultiPolygon
.