JavaScript - Geolocation API

Geolocation API

The Geolocation API is a web API that provides a JavaScript interface to access the user's geographical location data. A Geolocation API contains the various methods and properties that you can use to access the user's location on your website.

It detects the location of the user's using the device's GPS. The accuracy of the location depends on the accuracy of the GPS device.

As location compromises the users' privacy, it asks for permission before accessing the location. If users grant permission, websites can access the latitude, longitude, etc.

Sometimes, developers need to get the user's location on the website. For example, if you are creating an Ola, Uber, etc. type applications, you need to know the user's location to pick them up for the ride.

The Geolocation API allows users to share the location with a particular website.

Real-time use cases of the Geolocation API

Here are the real-time use cases of the Geolocation API.

To get the user's location coordinates, show them on the map.
To tag the user's location on the photograph.
To suggest nearby stores, food courts, petrol pumps, etc., to users.
To get the current location for the product or food delivery.
To pick up users for the ride from their current location.

Using the Geolocation API

To use the Geolocation API, you can use the 'navigator' property of the window object. The Navigator object contains the 'geolocation' property, containing the various properties and methods to manipulate the user's location.

Syntax

Follow the syntax below to use the Geolocation API.

var geolocation = window.navigator.geolocation;
OR
var geolocation = navigator.geolocation;

Here, the geolocation object allows you to access the location coordinates.

Example: Checking the browser support

Using the navigator, you can check whether the user's browser supports the Geolocation.geolocation property.

The code below prints the message accordingly whether the Geolocation is supported.

First, we convert the data into the JSON format. After that, we convert the data into the string and print it on the web page.

<html>
<body>
  <div id = "output"> </div>
  <script>
    const output = document.getElementById("output");
    if (navigator.geolocation) {
      output.innerHTML += "Geolocation is supported by your browser."
    } else {
      output.innerHTML += "Geolocation is not supported by your browser."
    }
  </script>
  </body>
</html>

Output

Geolocation is supported by your browser.

Geolocation Methods

Here are the methods of the Geolocation API.

Method	Description
getCurrentPosition()	It is used to retrieve the current geographic location of the website user.
watchPosition()	It is used to update the user's live location continuously.
clearWatch()	To clear the ongoing watch of the user's location using the watchPosition() method.

The Location Properties

The getCurrentPosition() method executes the callback function you passed as an argument. The callback function takes the object as a parameter. The parametric object contains various properties with information about the user's location.

Here, we have listed all properties of the location object in the table below.

Property	Type	Description
coords	objects	It is an object you get as a parameter of the callback function of the getCurrentPosition() method. It contains the below properties.
coords.latitude	Number	It contains the latitude of the current location in decimal degrees. The value range is [-90.00, +90.00].
coords.longitude	Number	It contains the longitude of the current location in decimal degrees. The value range is [-180.00, +180.00].
coords.altitude	Number	It is an optional property, and it specifies the altitude estimate in meters above the WGS 84 ellipsoid.
coords.accuracy	Number	It is also optional and contains the accuracy of the latitude and longitude estimates in meters.
coords.altitudeAccuracy	Number	[Optional]. It contains the accuracy of the altitude estimate in meters.
coords.heading	Number	[Optional]. It contains information about the device's current direction of movement in degrees counting clockwise relative to true north.
coords.speed	Number	[Optional]. It contains the device's current ground speed in meters per second.
timestamp	date	It contains the information about the time when the location information was retrieved, and the Position object created.

Getting User's Location

You can use the getCurrentPosition() method to get the user's current location.

Syntax

Users can follow the syntax below to get the user's current position using the getCurrentPosition() method.

navigator.geolocation.getCurrentPosition(successCallback, errorCallback, options);

Parameters

The getCurrentPosition() object takes 3 parameters.

successCallback − This function will be called when the method successfully retrieves the user's location.
errorCallback − This function will be called when the method throws an error while accessing the user's location.
Options − It is an optional parameter. It is an object containing properties like timeout, maxAge, etc.

Permitting the website to access your location

Whenever any website tries to access your location, the browser pops up the permission alert box. If you click the 'allow’, it can fetch your location details. Otherwise, it throws an error.

You can see the permission pop-up in the image below.

Example

In the below code, we use the getCurrentPosition() method to get the user's location. The method calls the getCords() function to get the current location.

In the getCords() function, we print the value of the various properties of the cords object.

First, we convert the data into the JSON format. After that, we convert the data into the string and print it on the web page.

<html>
<body>
  <h3> Location Information </h3>
  <button onclick = "findLocation()"> Find Location </button>
  <p id = "output"> </p> 
  <script>
    const output = document.getElementById("output");
    function findLocation() {
      if (navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(getCords); //
      }
      else {
        output.innerHTML += "Geo Location is not supported by this browser!";
      }
    }
    // Callback function
    function getCords(coords) {
      output.innerHTML += "The current position is: <br>";
      output.innerHTML += "Latitude: " + coords.coords.latitude + "<br>";
      output.innerHTML += "Longitude: " + coords.coords.longitude + "<br>";
      output.innerHTML += "Accuracy: " + coords.coords.accuracy + "<br>";
      output.innerHTML += "Altitude: " + coords.coords.altitude + "<br>";
    }  
  </script>
</body>
</html>

Geolocation Errors

The getCurrentPosition() method takes the callback function as a second parameter to handle the error. The callback function can have an error object as a parameter.

In the below cases, an error can occur.

When the user has denied access to the location.
When location information is not available.
When the request for the location is timed out.
It can also generate any random error.

Here is the list of properties of the error object.

Property	Type	Description
code	Number	It contains the error code.
message	String	It contains the error message.

Here is the list of different error codes.

Code	Constant	Description
0	UNKNOWN_ERROR	When methods of the geolocation object can’t retrieve the location, it returns the code 0 for unknown error.
1	PERMISSION_DENIED	When the user has denied the permission to access the location.
2	POSITION_UNAVAILABLE	When it can’t find the location of the device.
3	TIMEOUT	When the method of the geolocation object can’t find the user’s position.

Example: Error Handling

We use the getCurrentPosition() method in the findLocation() function in the below code. We have passed the errorCallback() function as a second parameter of the getCurrentPosition() method to handle the errors.

In the errorCallback() function, we use the switch case statement to print the different error messages based on the error code.

When you click the Find Location button, it will show you a pop-up asking permission to access the location. If you click on the 'block’, it will show you an error.

First, we convert the data into the JSON format. After that, we convert the data into the string and print it on the web page.

<html>
<body>
<div id = "output"> </div>
<button onclick = "findLocation()"> Find Location </button>
<script>
const output = document.getElementById("output");
function findLocation() {
  if (navigator.geolocation) {
    navigator.geolocation.getCurrentPosition(getCords, errorCallback); //
  }
  else {
    output.innerHTML += "Geo Location is not supported by this browser!";
  }
}
// Callback function
function getCords(coords) {
  output.innerHTML += "The current position is: <br>";
  output.innerHTML += "Latitude: " + coords.coords.latitude + "<br>";
  output.innerHTML += "Longitude: " + coords.coords.longitude + "<br>";
}
// Function to handle error
function errorCallback(err) {
  switch (err.code) {
    case err.PERMISSION_DENIED:
      output.innerHTML += "You have denied to access your device's location";
      break;
    case err.POSITION_UNAVAILABLE:
      output.innerHTML += "Your position is not available.";
      break;
    case err.TIMEOUT:
      output.innerHTML += "Request timed out while fetching your location.";
      break;
    case err.UNKNOWN_ERROR:
      output.innerHTML += "Unknown error occurred while fetching your location.";
      break;
  }
}  
</script>
</body>
</html>

Geolocation Options

The getCurrentPosition() method takes the object containing the options as a third parameter.

Here is the list of options you can pass as a key to the option object.

Property	Type	Description
enableHighAccuracy	Boolean	It represents whether you want to get the most accurate location.
timeout	Number	It takes a number of milliseconds as a value for that much time you want to wait to fetch the location data.
maximumAge	Number	It takes the milliseconds as a value, specifying the maximum age of the cached location.

Example

The below code finds the most accurate location. Also, we have set milliseconds to the maximumAge, and timeout properties of the options object.

First, we convert the data into the JSON format. After that, we convert the data into the string and print it on the web page.

<html>
<body>
<div id = "output"> </div>
<button onclick = "findLocation()"> Find Location </button>
<script>
  const output = document.getElementById("output");
  function findLocation() {
    if (navigator.geolocation) {
      // Options for geolocation
      const options = {
        enableHighAccuracy: true,
        timeout: 5000,
        maximumAge: 0
      };
      navigator.geolocation.getCurrentPosition(getCords, errorfunc, options);
    }
    else {
      output.innerHTML += "Geo Location is not supported by this browser!";
    }
  }
  // Callback function
  function getCords(coords) {
    output.innerHTML += "The current position is: <br>";
    output.innerHTML += "Latitude: " + coords.coords.latitude + "<br>";
    output.innerHTML += "Longitude: " + coords.coords.longitude + "<br>";
  }
  function errorfunc(err) {
    output.innerHTML += "The error message is - " + err.message + "<br>";
  }
</script>
</body>
</html>

Watching the Current Location of the User

The watchPosition() method allows you to track the live location of users. It returns the ID, which we can use with the clearWatch() method when you want to stop tracking the user.

Syntax

Follow the syntax below to use the watchPosition() method to track the live location of users.

var id = navigator.geolocation.watchPosition(successCallback, errorCallback, options)

The errorCallback and options are optional arguments.

If you want to stop tracking the user, you can follow the syntax below.

navigator.geolocation.clearWatch(id);

The clearWatch() method takes the id returned by the watchPosition() method as an argument.

Example

In the below code, we used the geolocation object's watchPosition () method to get the user's continuous position.

We used the getCords() function as a callback of the watchPosition() method, where we print the latitude and longitude of the user's position.

In the findLocation() method, we used the setTimeOut() method to stop tracking after 30 seconds.

In the output, you can observe that the code prints the user's position multiple times.

First, we convert the data into the JSON format. After that, we convert the data into the string and print it on the web page.

<html>
<body>
  <button onclick = "findLocation()"> Find Location </button>
  <div id = "output"> </div>
  <script>
    let output = document.getElementById("output");
    function findLocation() {
      if (navigator.geolocation) {
        let id = navigator.geolocation.watchPosition(getCoords);
        setTimeout(function () {
          navigator.geolocation.clearWatch(id);
          output.innerHTML += "<br>Tracking stopped!";
        }, 30000); // Stop tracking after 30 seconds.
      } else {
        output.innerHTML += "<br>Geo Location is not supported by this browser!";
      }
    }
    // Callback function
    function getCoords(location) {
      let latitude = location.coords.latitude;
      let longitude = location.coords.longitude;
      output.innerHTML += `<br> Latitude: ${latitude}, Longitude: ${longitude}`;
    }
  </script>
</body>
</html>

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