gistfile1.js

function just(x){ return {just: x}; }
var nothing = {nothing: null};
function maybe(d, f, m){
  if('nothing' in m){
    return d;
  }
  else if('just' in m){
    return f(m.just);
  }
  else{
    throw new Exception("invalid maybe value");
  }
}

function >>=(m, f){
  if('nothing' in m){
    return nothing;
  }
  else if('just' in m){
    return f(m.just);
  }
  else{
    throw new Exception("invalid maybe value");
  }
}