cps.bf.js

function bf (code) {
  var codeSize = code.length;
  var ip = 0, cp = 0, dp = 0, m = {};

  var loopIn = {}
    , loopOut = {}
    , tmp = [];

  for (cp = 0; cp < codeSize ; cp++)
    if (code[cp] == '[') tmp.push(cp);
    else if (code[cp] == ']') loopOut[loopIn[cp] = tmp.pop()] = cp;
 
  var ops = {
    '>': function () { dp++; runNext();}
  , '<': function () { dp--; runNext();}
  , '+': function () {m[dp] = ((m[dp]||0)+1)&255; runNext();}
  , '-': function () {m[dp] = ((m[dp]||0)-1)&255; runNext();}
  , '.': function () {console.log(String.fromCharCode(m[dp])); runNext();}
  , ',': function () {
    console.input(function (data) {
      m[dp] = data.charCodeAt(ip++) || 0; 
      runNext();
    });
  }
  , '[': function () {m[dp]||(cp=loopOut[cp]); runNext();}
  , ']': function () {cp = loopIn[cp]-1; runNext();}
  };
  
  function noop () {}
  function runNext () {
    cp++;
    if (cp < codeSize) {
      (ops[code[cp]] || noop)();
    }
  }
  cp = -1;
  runNext();
}