geojson

Convert an array of geographic objects to GeoJSON

npm install geojson
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GeoJSON.js

Convert an array of objects with geometry to a GeoJSON feature collection.

Installation

For node, use npm: $ npm install geojson

In the browser, include geojson.min.js. For example: <script type="text/javascript" src="js/geojson.min.js"></script>

Getting Started

In node, var GeoJSON = require('geojson');

In the browser, the library is available at GeoJSON.

Example Usage

The library has one method, parse, which takes an array of objects with geometry data as the first parameter, an object consisting of settings for the second parameter, and an optional callback function as the third parameter. If a callback is not specified, the parse function returns the GeoJSON output.

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']}, function(geojson){
  console.log(JSON.stringify(geojson));
});

  { 
    "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']}, function(geojson){
  console.log(JSON.stringify(geojson));
});

  { 
    "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"
        }
      }
    ]
  }

Convert the example data to GeoJSON, and include some dataset attributes.

GeoJSON.parse(data, {Point: ['lat', 'lng'], attrs: {'Creator': 'Mr. Example', 'records': data.length, 'summary': 'A few example points'}}, function(geojson){
  console.log(geojson);
});

  { 
    "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"
        }
      }
    ],
    "Creator": "Mr. Example",
    "records": 2,
    "summary": "A few example points"
  }

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'}, function(geojson){
  console.log(JSON.stringify(geojson));
});

{
  "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, {}, function(geojson){
  console.log(JSON.stringify(geojson));
});

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Point",
        "coordinates": [-75, 34]
      },
      "properties": {
        "name": "Location A"
      }
    }
  ]
}

GeoJSON.parse(data2, {}, function(geojson){
  console.log(geojson.js)
});

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Point",
        "coordinates": [-98, 54]
      },
      "properties": {
        "name": "Location B"
      }
    }
  ]
}

If you specify a callback function, the GeoJSON output is set as the first parameter of the function

GeoJSON.parse(data, {Point: ['lat', 'lng']}, function(geojson){
  console.log(JSON.stringify(geojson));
});

Parameters

include/exclude

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)

Geometry

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']});

or

data = [{ name: 'location', coords: [85, 34] }];

GeoJSON.parse(data, {Point: 'coords'});

The valid geometry types are

  • Point
  • MultiPoint
  • LineString
  • MultiLineString
  • Polygon
  • MultiPolygon

bbox, crs

geojson.js also supports the optional GeoJSON properties bbox and crs.

  • crs - A string identifying a coordinate reference system. Only named CRSs are supported at the moment. More information
  • bbox - A bounding box for the feature collection. An array with the following format: [y1, x1, y2, x2]. More information

extra

You can add arbitrary properties to features using the extra param. The value for extra must be an object. For example, using the original sample data:

GeoJSON.parse(data, {
  Point: ['lat', 'lng'],
  extra: {
    style: {
      "color": "#ff7800",
      "weight": 5,
      "opacity": 0.65
    }
  }
},
  function(geojson){
    console.log(JSON.stringify(geojson));
});

{ 
  "type": "FeatureCollection",
  "features": [
    { "type": "Feature",
      "geometry": {"type": "Point", "coordinates": [-75.343, 39.984]},
      "properties": { 
        "name": "Location A",
        "category": "Store",
        "style": {
          "color": "#ff7800",
          "weight": 5,
          "opacity": 0.65
        }
      }
    },
  ...
}    

extraGlobal

You can also add dataset properties using the extraGlobal param. The value for extraGlobal must be an object. For example, see below:

GeoJSON.parse(data, {
  Point: ['lat', 'lng'], 
  extraGlobal: {
    'Creator': 'Mr. Example', 
    'records': data.length, 
    'summary': 'A few example points'
  }
}, function(geojson){
  console.log(geojson);
});

  { 
    "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"
        }
      }
    ],
    "properties": {
      "Creator": "Mr. Example",
      "records": 2,
      "summary": "A few example points"
    }
  }

Tests

For node, $ npm test.

For the browser, visit test/test.html.

Building

$ grunt will run test.js, then lint and minify geojson.js.

$ grunt all will do all the above, plus run the browser tests, test.html. Note that this requires PhantomJS.

License

Licensed under the MIT License. See LICENSE for details.

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