Node.js: Callback is returning an fault

function die(err) {
  console.log('Uh oh: ' + err);
  process.exit(1);
}

var box, cmds, next = 0, cb = function(err) {
  if (err)
    die开发者_Python百科(err);
  else if (next < cmds.length)
    cmds[next++].apply(this, Array.prototype.slice.call(arguments).slice(1));
};

cmds = [
  function() { imap.connect(cb); },
  function() { imap.openBox('INBOX', false, cb); },
  function(result) { box = result; imap.search([ 'UNSEEN', ['SINCE', 'April 5, 2011'] ], cb); },
  function(results) {
    var msgCache = {},
        fetch = imap.fetch(results, { request: { headers: ['from', 'to', 'subject', 'date'] } });
    console.log('Now fetching headers!');
    fetch.on('message', function(msg) {
      msg.on('end', function() {
        msgCache[msg.id] = { headers: msg.headers };
      });
    });
    fetch.on('end', function() {
      console.log('Done fetching headers!');
      console.log('Now fetching bodies!');
      fetch = imap.fetch(results, { request: { headers: false, body: '1' } });
      fetch.on('message', function(msg) {
        msg.data = '';
        msg.on('data', function(chunk) {
          msg.data += chunk;
        });
        msg.on('end', function() {
          msgCache[msg.id].body = msg.data;
        });
      });
      fetch.on('end', function() {
        console.log('Done fetching bodies!');
        cb(msgCache);
      });
    });
  },
  function(msgs) {
    // Do something here with msgs, which contains the headers and
    // body (parts) of all the messages you fetched
    console.log("HERE");
    imap.logout(cb);    
    
  }
];
cb();

I'm using that code to get the headers and the body of an e-mail. However, when I try to pass the result (msgCache) it gets an error.

What am I missing here?

It seems like you are calling cb(msgCache) in your fetch on end callback, and cb takes the first argument err. If err is a valid non empty object, then it will call your error handler and die, so it is calling the error handler even with a valid msgCache.

Why not call console.log(msgCache) instead of cb(msgCache) and see if you get through to the end ok.

Or am I missing the point where the error occurs?