Observations.js

Observations.js takes a string of simple JavaScript (one-liners, no blocks) and triggers the given callback whenever the result of the function changes. Using Expressions.js it deals with null values gracefully and supports formatters.

Usage

Basic

To install Observations.js you can use npm.

npm install observations-js

To use observations:

var observations = require('observations-js').create();
 
var observer = observations.createObserver('name', function(value) {
  console.log('Name is', value);
});
 
var person = { name: 'Bob' };
observer.bind(person);
// logged "Name is Bob"
 
person.name = 'Fred';
 
observations.syncNow();
// logged "Name is Fred"

API

Observations

• observations.createObserver(expression, callback, [callbackContext])
  • Registers a new observer and callback.
• observations.observeMembers(expression, addedCallback, removedCallback, [callbackContext])
  • Registers a new observer and calls the added callback whenever a member (of an array or object) is added and calls removed callback whenever a member is removed. Use obj.computedObservers.enable() or disable() to turn on/off.
• observations.computed(expressionMap)
  • Creates an object which keeps the results of the computed expression map in sync
• observations.computed.extend(obj, expressionMap)
  • Extends an existing object with the results of the computed expression map
• observations.sync([callback])
  • Diffs observed objects, calling the registered callback on changed objects on the next sync cycle.
• observations.syncNow([callback])
  • Explicitly runs the sync cycle on-demand.
• observations.afterSync(callback)
  • Registers a callback to fire after the next (or current) sync cycle completes.
• observations.onSync(listener)
  • Adds a listener that gets run during sync().
• observations.offSync(listener)
  • Removes an onSync listener.

Observer

• observer.bind(context)
• observer.unbind()
• observer.get()
• observer.set(value)
• observer.skipNextSync()
• observer.close()

Contributions and Issues

Please open a ticket for any bugs or feature requests.

Contributions are welcome. Please fork and send a pull-request.