Va Hender?!

Va Hender?! is a JavaScript statemachine.

Those are the features:

• Simple syntax.
• States are hierarchical.
• There is a root state. All other states are descendants from the root.
• Unit tested code.
• "Va Hender?!" is Swedish for "What's Up?!", spelled like we pronounce it in Stockholm.

Get started

This is kind of how it works:

var
	vh = require('vahender'),
	rootState = new vh.Root();

// Define two child states to the root state:
var alive = rootState.child('alive');
var dead = rootState.child('dead');

// Define four child states to the alive state:
var hungry = alive.child('hungry');
var satisfied = alive.child('satisfied');
var full = alive.child('full');
var sick = alive.child('sick');

// Define events to cause transitions:
hungry.eat = satisfied.enter; // Call hungry.eat() to get to satisfied state.

satisfied.eat = full.enter; // Call satisfied.eat() to get to full state.
satisfied.rest = hungry.enter; // Call satisfied.rest() to get to hungry state.

full.eat = sick.enter; // Call full.eat() to get to sick state.
full.rest = satisfied.enter; // Call satisfied.rest() to get to satisfied state.

sick.eat = dead.enter; // Call sick.eat() to get to dead state.
sick.rest = full.enter; // Call satisfied.rest() to get to full state.

// dead state has no transitions.

// Define event to start it all with:
rootState.birth = hungry.enter;

var transition = rootState.birth(); // Returns a Transition object!
transition.on('started', function () {
	console.log('Transition started.');
});
transition.on('aborted', function (reason) {
	console.log('Transition was aborted: ' + reason);
});
transition.on('finished', function () {
	console.log('Transition finished.');
});

// Add events to states:
full.on('enter', function() {
	console.log('You are full.');
});

alive.update = function (next) {
	// As long as alive (or any of alive's descendants) is the current state,
	// this will be called (often!)

	next(); // Must call the callback, or everything will stop.
};

State events

• enter - this state got activated.
• leave - this state got inactivated.
• newchild - this state got a new child. only emitted for children, not emitted for grandchildren. params: 1. the child state obj.
• current - this state is now the current state.
• childcurrent - some child became the current state. First argument is new the state object. Second argument is the old state object.

Note: There can only be one current state, but many activated states. When a state is current, it and all it's ancestors are activated.

Transition events

• started - this transition just started.
• aborted - this transition was aborted. First argument is the reason why (a string).
• finished - this transition just finished (successfully).

State properties

• .active - True if this state or any children/grandchildren/etc is the current state.
• .longname - The name of this state including breadcrubs from parent states.
• .name - The name of this state. (The string given at state creation.)
• .root - The root state object.
• .root.current - The current state.
• .parent - The parent of this state. Undefined if State is the root state.
• .parents - An array of parents, grand parents, and so on.

State methods

• .child(name, callback) - Creates a new child state. Returns the new child state object. If defined, the callback function will be called with the new child state object as the only argument.
• .hasParent(state) - True if this state is descendant to the given state. Otherwise false.

Transition properties

• .from - State to make transition from.
• .to - State to make transition to.

Change Log

• 1.1.0 - New feature: .child() has a callback.
• 1.0.1 - Bugfix: Only current state can initiate transition.
• 1.0.0 - Initial version.