Basic Turing Machine simulator in JS

TM.js

function TM(tape, alphabet, states, start){
	var state, transition, symbol,
		counter = 0, stateId = start, pos = 0;
	while(true){
		symbol = tape[pos];
		if(typeof symbol === 'undefined'){
			symbol = alphabet[0];
			tape[pos] = symbol;
		}
		state = states[stateId];
		transition = state?state[symbol]:void 0;
		console.log(++counter, stateId+'['+tape.slice(0,pos).join('')+'('+symbol+')'+ tape.slice(pos+1).join('')+']');
		debugger;
		if(!transition){
			return {
				accept: !!state.accept,
				tape: tape
			};
		}
		(transition.o||[]).forEach(function(op){
			if(op.hasOwnProperty('p')){
				tape[pos] = op.p
			}else if(op.hasOwnProperty('m')){
				pos += op.m == "R"? 1:-1;
				if(pos < 0){
					pos = 0;
					tape.unshift(alphabet[0]);
				}else if(tape[pos] == void 0){
					tape[pos] = alphabet[0];
				}
			}
		});

		stateId = transition.s;
	}
}

/* Run the 3-state Busy Beaver Machine on an empty tape */
TM([], ['0', '1'], {
	A: {
		0: {o: [{p: '1'}, {m: "R"}], s: "B"},
		1: {o: [{p: '1'}, {m: "L"}], s: "C"}
	},
	B: {
		0: {o: [{p: '1'}, {m: "L"}], s: "A"},
		1: {o: [{p: '1'}, {m: "R"}], s: "B"}
	},
	C: {
		0: {o: [{p: '1'}, {m: "L"}], s: "B"},
		1: {o: [{p: '1'}], s: "HALT"}
	},
	HALT: {accept:true}
}, "A");

TM([], [' ', 'e', 'x', '0', '1'], {
	b: {
		' ': {o: [{p:'e'},{m:"R"},{p:'e'},{m:"R"},{p:'0'},{m:"R"},{m:"R"},{p:'0'},{m:"L"},{m:"L"}], s: "o"}
	},
	o: {
		1: {o: [{m:"R"},{p:'x'},{m:"L"},{m:"L"},{m:"L"}], s: "o"},
		0: {o: [], s: "q"}
	},
	q: {
		0: {o: [{m:'R'},{m:'R'}], s: "q"},
		1: {o: [{m:'R'},{m:'R'}], s: "q"},
		' ': {o: [{p:'1'},{m:"L"}], s: "p"},
	},
	p: {
		x: {o: [{p:' '},{m:"R"}], s: "q"},
		e: {o: [{m:'R'}], s: "f"},
		' ': {o: [{m:"L"},{m:"L"}], s: "p"}
	},
	f: {
		0: {o: [{m:'R'},{m:'R'}], s: "f"},
		1: {o: [{m:'R'},{m:'R'}], s: "f"},
		x: {o: [{m:'R'},{m:'R'}], s: "f"},
		e: {o: [{m:'R'},{m:'R'}], s: "f"},
		' ': {o: [{p:'0'},{m:"L"},{m:"L"}], s: "o"}
	}
}, "b");