Example of functional programming in JavaScript

functional.js

// Example of how one might do some functional programming in 
// JavaScript. This example uses promises and presents a fictional
// process for taking a photo, creating a thumbnail, and saving 
// them.  Notice how the data is passed through all the functions
// instead of being stored in a higher scope.

obtainCamera()
.then(function(camera) {
 // we receive a camera from obtainCamera()
 
 camera.setZoom(5);
 camera.enableAutofocus(true);
 return camera.takePhoto();
})
.then(function(photo) {
 // we receive a photo as output from the previous function
 
 // we copy the photo and downsize it to become a thumbnail
 var thumbnail = photo.copy();
 thumbnail.resize(100, 100);
 
 // we return an object containing the original photo and the 
 // new thumbnail
 return {
  photo: photo,
  thumbnail: thumbnail
 }
})
.then(function(photos) {
 // we receive the photo and thumbnail, then we save them
 return getDatabase().save(photo);
});