Broken by promises

broken by promises

/**
I've been using promises a lot lately after my first dance in callback hell.

I have not read (but did skim) any of the specs nor do I intend too. I also find the bedtime stories about
promises cute but far to wordy when I'm in a hurry.

So I decided to type up this for future reference, when next time I chain some promises together and am completly confused as
to why they don't work the way I expect.

Think of promises like an asynchronous try, catch, finally
**/
//That is to say:

javascript

  loadWebPage().
  then(null, onLoadWebPageError).
  then(saveToDatabase).
  then(null, onSaveToDatabaseError).
  then(emailResults).
  then(null, onEmailSaveError).
  done(cleanup);
  


//if almost like saying:



try {

   loadWebPage();
   saveToDatabase();
   emailResults();
   catch(LoadWebPageException e) {
      onLoadWebPageError();
   }catch(SaveToDatabaseException e) {
     onSaveToDatabaseError();
   }catch(EmailResultsException e) {
    onEmailSaveError();
    }finally{
      cleanup();
    }




//Of course the above could be done in node except that almost all io is async so it won't quite work, that's why
//we use promises.