Introduction to Node-Geocoder

Node-Geocoder is an essential npm library for geocoding, offering a simple interface for converting an address into geographical coordinates (latitude and longitude) and vice versa. This comprehensive guide will explore various aspects of Node-Geocoder through dozens of useful examples and a practical application.

Basic Setup

  
    const NodeGeocoder = require('node-geocoder');

    const options = {
      provider: 'openstreetmap',
      // Optional depending on the providers.
      apiKey: 'YOUR_API_KEY',
      formatter: null // 'gpx', 'string', ...
    };

    const geocoder = NodeGeocoder(options);
  

Geocoding API Examples

Get Latitude and Longitude from Address

  
    geocoder.geocode('29 champs elysée paris')
      .then(function (res) {
        console.log(res);
      })
      .catch(function (err) {
        console.log(err);
      });
  

Reverse Geocoding: Get Address from Latitude and Longitude

  
    geocoder.reverse({ lat: 45.767, lon: 4.833 })
      .then(function (res) {
        console.log(res);
      })
      .catch(function (err) {
        console.log(err);
      });
  

Batch Geocoding

  
    geocoder.batchGeocode([
      '13 rue sainte catherine lyon', 
      'another address'
    ])
     .then(function (res) {
       console.log(res);
     })
     .catch(function (err) {
       console.log(err);
     });
  

Get Country from Latitude and Longitude

  
    geocoder.reverse({ lat: 48.8566, lon: 2.3522 })
      .then(function (res) {
        console.log(res[0].country);
      })
      .catch(function (err) {
        console.log(err);
      });
  

Customizing Results

Node-Geocoder also allows for custom formatting of results. Below is a simple demonstration on how to change the output format:

  
    const geocoder = NodeGeocoder({
      provider: 'openstreetmap',
      formatter: function(result) {
        return {
          formattedAddress: result.formattedAddress,
          latitude: result.latitude,
          longitude: result.longitude,
          extra: {
            timezone: result.extra.timezone,
          }
        };
      }
    });
  

Application Example

Let’s create a simple Node.js application that utilizes the Node-Geocoder library to geocode addresses and display them.

  
    const express = require('express');
    const NodeGeocoder = require('node-geocoder');
    
    const app = express();
    const port = 3000;
    
    const options = {
      provider: 'openstreetmap',
      apiKey: 'YOUR_API_KEY'
    };
    const geocoder = NodeGeocoder(options);
    
    app.get('/geocode', (req, res) => {
      const address = req.query.address;
      geocoder.geocode(address)
        .then(function (data) {
          res.json(data);
        })
        .catch(function (err) {
          res.status(500).send(err);
        });
    });

    app.listen(port, () => {
      console.log(`Server running on http://localhost:${port}`);
    });
  

In this simple application, you can pass an address as a query parameter to the /geocode endpoint, and it will return the geocoded data in JSON format.

Node-Geocoder is a powerful tool for any application that relies on geolocation data. With its simple API and support for various geocoding services, it can be easily integrated into a wide range of applications.

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