A practical example of closures in JavaScript: creating custom loggers.

gistfile1.js

function getLogger(prefix) {
  return function(message) {
    console.log(prefix + ": " + message);
  }
}

// Video component
(function() {
  log = getLogger("video");
  log("initialized");

  // do some video stuff
  log("h264 3022kbit/s");
})();


// Audio component
(function() {
  log = getLogger("audio");
  log("initialized");

  // do some audio stuff
  log("48khz stereo");
})();