A reactive, modern JavaScript library for general purpose finite state machines with support for navigation and routing.
This state machine
library can be used to track the states and model state transitions of
- business objects,
- application status,
- proccess flows,
- and many more.
Using finite state machine models helps to structure and reason about problems. It supports creating maintainable business rules and source code. Use the state machine diagrams to communicate behaviour and requirements.
Examples:
-
Task Management: Once a task is
pending
, it can beassigned
,completed
, orcanceled
. An email is send out to the assinged person. -
Flight status: A plane is
IN
the gate and then is pushedOUT
. OnceON
the runway, the plane takesOFF
from the origin airport to landON
at the destination.
Using node/webpack/rollup/browserify:
npm install ea-state-machine
And, if you have not already, install the only peer dependency rxjs
.
npm install rxjs
Defining set of possible States.
import { FSM } from 'ea-state-machine'
const state = {
solid: { name: 'Ice' },
liquid: { name: 'Water' },
gas: { name: 'Vapor' }
}
Guards prevent transitions by returning false
const guard = {
canMelt: (fsm, from, to) => fsm.data.temperature > 0,
canVaporize: (fsm, from, to) => fsm.data.temperature > 100,
canCondense: (fsm, from, to) => fsm.data.temperature < 100,
canFreeze: (fsm, from, to) => fsm.data.temperature >= 0
}
Transition Definitions can be from many to many
const transitionDefiniton = {
melt: {
from: state.solid, // can be a single state
to: [state.liquid], // or multiple targets
guards: [guard.canMelt],
action: () => console.log('melting ...'),
},
vaporize: {
from: () => [state.liquid],
to: () => [state.gas],
action: () => console.log('vaporizing ...'),
guards: [guard.canVaporize],
},
condense: {
from: () => [state.gas],
to: () => [state.liquid],
guards: [guard.canCondense],
action: () => console.log('condenseing ...'),
},
freeze: {
from: () => [state.liquid],
to: () => [state.solid],
guards: [guard.canFreeze],
action: () => console.log('freezing ...'),
},
}
Using the above state machine.
// data associated with the fsm
const environment = {
temperature: 0
}
const fsm = new FSM(
state, // all states
transitionDefiniton, // transition defitions between states
state.solid, // optional: start state, if omitted, a transition to the first state needs to happen
environment // optional: associated data with the state machine
)
fsm.currentState === fsm.states.solid // true
// Can we melt?
fsm.canTranstionTo(fsm.statesliquid) // false
// Heat and update FSM
fsm.changeData({ environment.temperature = 4})
fsm.canTranstionTo(fsm.states.liquid) // true
fs.transtionTo(fsm.states.liquid)
// // different ways with same effect as above
// fsm.transitionByDefinition(transitionDefiniton.melt)
// fsm.transition(fsm.transitions.filter(t => t.to === fsm.states.liquid))
fsm.currentState.name === 'Water' // true
TODO: One page per example