Ambitious data-flow library.

Install the module with: npm install menrva

var menrva = require('menrva');
menrva.some('awe'); // some, as in awesome?

The core type of menrva. Signal is abstract class, and cannot be created explicitly.

Similar concepts are: Behaviours in FRP, Properties in bacon.js.

You can add methods to Signal's prototype. They will be available on all signals.

map (@ : Signal a, f : a -> b, eq = egal : b -> b -> boolean) : Signal b

onValue (@ : Signal a, callback : a -> void) -> Unsubscriber

Add value callback. callback is immediately executed with the current value of signal. After than callback will be called, each time signal's value changes.

The return value is a function, which will remove the callback if executed.

value (@ : Signal a): Signal a

Returns the current value of signal.

A signal which value you can set.

Similar concepts are: Bacon.Model in bacon.js, BehaviourSubject in Rx.

source (initialValue : a, eq = egal : a -> a -> boolean) : Source a

set (@ : Source a, tx : Transaction, value : a) : void

modify (@ : Source a, tx : Transaction, f : a -> a) : void

Mofify source value. f will be called with current value of signal inside the transaction.

combine (Signal a..., f : a... -> b) : Signal b

Applicative n-ary lift. Lift pure function to operate on signals:

var $sum = menrva.combine($a, $b, function (a, b) {
  return a + b;
});

One gathers atomic updates into single transaction (to avoid glitches).

var tx = menrva.transaction();
sourceA.set(tx, 42);
sourceB.modify(tx, function (x) { return x + x; });
tx.commit(); // not necessary, transactions are auto-commited

There are also optional syntaxes for simple transactions:

menrva.transaction()
  .set(sourceA, 42)
  .modify(sourceB, function (x) { return x + x; })
  .commit();

or even

menrva.transaction([sourceA, 42, sourceB, function(x) { return x + x; }]).commit();

transaction (facts) : Transaction

Create transaction.

Shorthand syntax:

transaction ([sourceA, valueA, sourceB, valueB ...]) : Transaction

If value is function, source.modify(tx, value) is called; otherwise source.set(tx, value).

Commit the transaction, forcing synchronous data propagation.

Rollback the transaction. Maybe be called multiple times (consecutives calls are no-op).

Note: for now rollback only resets the pending actions in transactions. Transaction is still valid, and more actions can be added

Lenses are composable functional references. They allow you to access and modify data potentially very deep within a structure!

zoom (@ : Source a, path : Path a b, eq = egal : b -> b -> boolean) : Source b

Zoom (or focus) into part specified by path of the original signal. One can set and modify zoomed signals, they act as sources.

var quux = source.zoom("foo.bar.quux");

signal.log (@ : Signal a, args...) : Unsubscriber

Essentially `signal.onValue(console.log.bind(console, args...))

signal.onSpread (@ : Signal [a, b...], callback : a -> b ... -> void) : Unsubscriber

onValue with signal's tuple arguments spread.

tuple (x : Signal a, y : Signal b...) : Signal [a, b...]

Combine signals into tuple.

sequence [Signal a, Signal b, ..] : Signal [a, b...]

In promise libraries this might be called all.

record {k: Signal a, l: Signal b...} : Signal {k: a, l: b...}

Like sequence but for records i.e. objects.

egal (a, b) : boolean

Identity check. Object.is. http://wiki.ecmascript.org/doku.php?id=harmony:egal

Also known as Maybe.

equals (@ : option a, other : *, eq = eqal : a -> a -> boolean) : boolean

Equality check.

map (@ : option a, f : a -> b) : option b

elim (@ : option a, x : b, f : a -> b) : b

orElse (@ : option a, x : a) : a

In lieu of a formal styleguide, take care to maintain the existing coding style.

Add tests for any new or changed functionality. 100% coverage isn't hard. Semantic coverage is important too though.

Note: README.md is autogenerated file.

• 0.0.7 sequence and record
• 0.0.6 Convenience methods
• 0.0.5 Lens
• 0.0.4 Internal improvements
• 0.0.3 Slight changes in API
• 0.0.2 Basic data-flow functionality
• 0.0.1 Name reservation

Copyright (c) 2014 Oleg Grenrus. Licensed under the MIT license.