RxJS Release v2.2.18

Update from RxJS v2.2.17 to include the following changes.

Helper Functions

In order to facilitate people using default parameters, RxJS exports helper functions in the Rx.helpers object including:

• noop - No operation
• identity - Passthrough function which returns the parameter value.
• defaultNow - Default function for getting the current time.
• defaultComparer - Default comparer which uses the interval Rx.internals.isEqual function.
• defaultSubComparer - Default comparer for using comparisons of greater than, less than or equal to.
• defaultKeySerializer Default key serializer function which calls .toString by default.
• defaultError - Throws the given error
• isPromise - Used to detect whether the given object is a Promise.
• asArray- Converts the arguments of the function into an array.
• not - Returns the opposite of the current function's return value.

More Promises Support

In addition to the previous support for Promises from the previous release for flatMap/selectMany,we have now extended it to the following:

• Rx.Observable.catch
• Rx.Observable.concat
• Rx.Observable.defer

An example for defer would look like the following:

// Concat on Promises to execute sequentially
var promises = [ur1, url2, url3].map(function (url) {
  // Ensure we don't fire each until it is subscribed
  return Rx.Observable.defer(function () { 
    return getJSON(url); 
  });  
});

var sources = Rx.Observable.concat(promises).toArray();
sources.subscribe(function (results) {
  // Get all the results as an array
});

In addition, this works with concat such as the following:

/* Concat as arguments */
var sources = Rx.Observable.concat(promise1, promise2, promise3);

/* Concat as an array */
var sources = Rx.Observable.concat([promise1, promise2, promise3]);

/* Concat on an Observable */
var newSource = source.concat(promise1);

In addition, this works nicely with catch as well.

/* Catch as arguments */
var sources = Rx.Observable.catch(promise1, promise2, promise3);

/* Catch as an array */
var sources = Rx.Observable.catch([promise1, promise2, promise3]);

/* Catch on an Observable */
var newSource = source.catch(promise1);

As time goes on, we'll also be looking at other areas for support for promises within RxJS.