JS Geolocation API – getCurrentPosition with options parameter

In the last post (JS Geolocation API – Get a User's Location) we have covered navigator.geolocation.getCurrentPosition() method to get user's location. We have used the success and error callbacks to receive the position object or report error.

The method getCurrentPosition() also accepts an options object as third paramter (optional).

This options object allows you to specify:

• enableHighAccurancy (default false): if set to true, response is slower and more accurate.
• maximumAge (default 0): milliseconds when cached value is valid, the device may decide to use valid cached data instead of sensor measure. Represents age for the returned position value (up until this age it will be cached and reused if the same position is requested again, after this the browser will request fresh position data)
• timeout (default infinity): milliseconds before the API gives up and calls the error handler (the second parameter).

The example below calls getCurrentPosition() with both success and error callbacks, and pass the options object in third argument:

var options = {
  enableHighAccuracy: true,
  timeout: 5000, //timeout 5 seconds
  maximumAge: 10000 //(location) age 10 seconds
};

navigator.geolocation.getCurrentPosition(success, error, options);

Related Post(s):

• JS Geolocation API – Get a User's Location

JS Geolocation API – Get a User's Location

The JavaScript Geolocation API provides access to geographical location data associated with a user's device. This can be determined using GPS, WIFI, IP Geolocation and so on.

Geolocation is most accurate for devices with GPS, like smartphones.

To protect the user's privacy, it requests permission to locate the device. If the user grants permission, you will gain access to location data such as latitude, longitude, altitude and speed etc.

The Geolocation API is available through the navigator.geolocation object.

If the object exists, geolocation services are available. You can test for the presence of geolocation:

if ("geolocation" in navigator) {
  console.log("geolocation is available");
} else {
  console.log("geolocation is not available");
}

navigator.geolocation object provides the method getCurrentPosition() to return the user's position.

There are three possible arguments with this method:

• A success callback (required)
• An error callback (optional)
• An options object (optional)

The example below calls getCurrentPosition() with both success and error callbacks, and returns the latitude and longitude of the user's position:

function getLocation() {
  if (navigator.geolocation) {
    navigator.geolocation.getCurrentPosition(usePositionData, useError);
  } else {
    console.log("Geolocation is not supported by this browser.");
  }
}

function usePositionData(position) {
	//do something with position data.
	console.log("Latitude: " + position.coords.latitude);
	console.log("Longitude: " + position.coords.longitude);
}

function useError(error) {
  switch(error.code) {
    case error.PERMISSION_DENIED:
      console.log("User denied the request for Geolocation.");
      break;
    case error.POSITION_UNAVAILABLE:
      console.log("Location information is unavailable.");
      break;
    case error.TIMEOUT:
      console.log("The request to get user location timed out.");
      break;
    case error.UNKNOWN_ERROR:
      console.log("An unknown error occurred.");
      break;
  }
}

Related Post(s):

• JS Geolocation API – getCurrentPosition with options parameter

CSS - Using media query features

Media Query features define the style for specific characteristics of a given user agent, output device, or environment.

Media features can be either range or discrete.

Discrete features take their value from an enumerated set of possible keyword values. For example, the discrete orientation feature accepts either landscape or portrait.

@media print and (orientation: portrait) {
  colod: red;
}

Many range features can be prefixed with min- or max- to express "minimum condition" or "maximum condition" constraints. For example, this CSS will apply styles only if your browser's viewport width is equal to or narrower than 1000px:

@media (max-width: 1000px) {
  colod: blue;
}

An alternative syntax for above condition is to use ordinary mathematical comparison operators >, <, >=, or <=.

@media (width <= 1000px) {
  colod: blue;
}

@media (width <= 1000px) is the equivalent of @media (max-width: 1000px).

These are some other commonly used media features:

• orientation: Orientation of the viewport (landscape or portrait)
• max-height: Maximum height of the viewport
• min-height: Minimum height of the viewport
• height: Height of the viewport (including scrollbar)
• max-width: Maximum width of the viewport
• min-width: Minimum width of the viewport
• width: Width of the viewport (including scrollbar)

Related Post(s):

• CSS - Using media queries

CSS - Using media queries

Media queries allow you to conditionally apply CSS styles depending on a device's media type (such as screen, print). You can also specifiy other features or characteristics such as screen resolution or orientation etc.

A media query is composed of an optional media type and any number of media feature expressions, which may be combined using logical operators.

Media types describe the general category of a given device, mainly we are using three basic types screen, print, and all.

• screen: used for websites commonly designed (for computer screens, tablets, smart-phones etc).

  @media screen {
    colod: red;
  }
  

• print: used for printing (print preview mode)

  @media print {
    colod: blue;
  }
  

• all: for all devies, there is no filter for any specific device category.

  @media all {
    colod: green;
  }
  

The mediatype is optional (if omitted, it will be set to all).

@media {
  colod: green;
}

You can also target multiple devices types. For instance, this @media rule uses two media queries to target both screen and print devices:

@media screen, print {
  colod: green;
}

Related Post(s):

• CSS - Using media query features

git shows files as modified after adding to .gitignore

In Visual Studio, once the .Net project is setup with git, you might notice that it will keep track for extra files, like autogenerated files in obj/debug folders.

You can ignore these selected folders/files by using .gitignore file.

To ignore debug, release, bin and obj folders etc., you can make these entries in .gitignore file.

[Dd]ebug/
[Rr]elease/
[Bb]in/
[Oo]bj/

After settings these changes you might notice that git is still tracking the files in these folders.

The reason is that these are the changes before the .gitignore file is updated.

To fix this issue you need to removes all files that have been cached (as being 'tracked'), then re-add files based on the .gitignore file entries.

Here are the steps, notice the dot (.) in the end of first 2 commands, this . is part of command syntax:

• Remove all files recursively from index that are cached (being tracked).

  git rm -r --cached .
  

  rm is to remove files, -r is to remove recursively.

• Add all files that have changed (re-add the files). This command will add all files except those which are mentioned in .gitignore.

  git add .
  

• This command will commit your files again and remove the files you want to ignore, but keep them in your local directory.

  git commit -am "Remove ignored files"