決定性有限オートマトン（っぽいの）

dfa.js

'use strict';

let DFA = class {
	constructor () {
		this.states = [];
		this.cursor = null;
		this.acceptedState = null;
	}
	addState (state) {
		if (this.states.length === 0) {
			this.cursor = state;
		}
		if (state.acceptedState) {
			this.acceptedState = state;
		}
		this.states.push(state);
	}
	read (string) {
		for (let character of string) {
			for (let rule of this.cursor.rules) {
				if (character === rule.character) {
					this.cursor = rule.destination;
				}
			}
		}
	}
	get accepting () {
		return this.cursor === this.acceptedState;
	}
}

let State = class {
	constructor (acceptedState) {
		this.rules = [];
		this.usedCharacters = [];
		this.acceptedState = acceptedState;
	}
	addRule (rule) {
		if (this.usedCharacters.indexOf(rule.character) !== -1) {
			throw new Error('決定性がないぞ〜（＾＾）');
		}
		this.rules.push(rule);
		this.usedCharacters.push(rule.character);
	}
}

let Rule = class {
	constructor (character, destination) {
		this.character = character;
		this.destination = destination;
	}
}

let dfa = new DFA();

let state1 = new State();
let state2 = new State();
let state3 = new State(true);

state1.addRule(new Rule('b', state1));
state1.addRule(new Rule('a', state2));

state2.addRule(new Rule('a', state2));
state2.addRule(new Rule('b', state3));

state3.addRule(new Rule('a', state3));
state3.addRule(new Rule('b', state3));

dfa.addState(state1);
dfa.addState(state2);
dfa.addState(state3);

dfa.read('bbbbab');

console.log(dfa.accepting);