nodejs parallel control flow by bitwise operation

gistfile1.js

var _a=0x01, _b=0x02, _c=0x04, _d=0x08, _e=0x10, _f=0x20, _done=0;

var triggers = [

  function(){
    // a,b 完成后，执行 d，execute d() when a and b done.
    if(_done & (_a | _b)){
      triggers.splice(triggers.indexOf(this), 1);
      d(function(){
          _done |= _d;
          process.nextTick(trigger);
      });
    }
  },
  function(){
    // b,c 完成后，执行 e，execute e() when b and c done.
    if(_done & (_b | _c)){
      triggers.splice(triggers.indexOf(this), 1);
      e(function(){
          _done |= _e;
          process.nextTick(trigger);
      });
    }
  },
  function(){
    // a,c 完成后，执行 f，execute f() when a and c done.
    if(_done & (_a | _c)){
      triggers.splice(triggers.indexOf(this), 1);
      f(function(){
          _done |= _f;
          process.nextTick(trigger);
      });
    }
  },
  function(){
    // 全部完成，all done
    if(_done & (_d |_e | _f)){
      triggers.splice(triggers.indexOf(this), 1);
      g(function(){
          console.log('end of control flow');
      });
    }
  }
];

function trigger(){
  for(var i=triggers.length -1;i>=0;i--){
    triggers[i]();
  }
}

a(function(){
    _done |= _a;
    process.nextTick(trigger);
});

b(function(){
    _done |= _b;
    process.nextTick(trigger);
});

c(function(){
    _done |= _c;
    process.nextTick(trigger);
});