A small state machine library

This is a javascript port of this library. The difference is this retains a tiny feature set of the original python implementation providing only the core and some other things. The user can extend it to their needs if they so desire.

Usage

import { StateMachine } from './state_machine.js';
class Model {
  constructor() {
    this.machine = new StateMachine(
      this,
      ['asleep', 'hangingOut', 'hungry', 'sweaty', 'savingTheWorld'],
      'asleep'
    );
    this.machine.addTransition({
      trigger: 'wakeUp',
      source: 'asleep',
      dest: 'hangingOut',
    });
    this.machine.addTransition({ trigger: 'nap', source: '*', dest: 'asleep' });
  }
}

The core is just a addTransition function to add state transitions (these can also be added as a parameter to the StateMachine constructor. The signature of the function is:

/**
 * @param {string} trigger - trigger function name.
 * @param {string} source - valid source state.
 * @param {string} dest - valid destination state.
 * @param {string} before - function to run before state transition.
 * @param {string} after - function to run after state transition.
 * @param {string[]} conditions - abort if any of the functions returns false.
 * @param {string[]} unless - abort if any of the functions returns true.
 */
export type Transition = {
  trigger: string;
  source: string;
  dest: string;
  before?: string;
  after?: string;
  conditions?: string[];
  unless?: string[];
};

Check the typescript declaration file for more details. Example programs can be found in the examples directory

For every state someState methods such as:

• isSomeState (is the current state someState)
• onEnterSomeState (fired every time we enter someState, except at the very beginning)
• onExitSomeState (fired every time we leave someState) are added on initialization. It is recommended to not use spaces between state names to avoid awkward method calls at runtime (this.isSomeState() instead of this['isSome State'])

Credits

pytransitions/transitions for the state machine core and also some examples

LICENSE

MIT