Async node.js data flow confusion

问题

thanks for your help...struggling big time with how to handle this properly. I'm in async now, having given up on my ability to write the callbacks properly. I have snippet where I'm passing a set of random numbers (eachrecord) and passing them through to a mongoose call. Trying to create a data set from the multiple queries I pass.

My issue is that no matter what I've done for 4 hours, the "newarray" variable is always empty.

Thank you for your help -

async.forEach(arLimit, function(eachrecord, callback){

  newarray = new Array;

  var query = UGC_DB_Model.find({}).skip(eachrecord).limit(-1);

  query.execFind(function (err, data) {
    if (err)
      console.log(err);
    else {
      newarray.push(data);
    }
  });

   callback(null, newarray);

}, function(err, result) {
  if (err) return next(err);
      console.log("(it's empty): " + result); 
}); 

回答1:

There are several issues with your code:

• async.forEach isn't meant to 'generate' results, that's what async.map is for;
• you need to call the callback only when execFind is done, and not immediately after calling it;
• your newarray is probably not necessary;

So try this instead:

async.map(arLimit, function(eachrecord, callback){

  var query = UGC_DB_Model.find({}).skip(eachrecord).limit(-1);

  query.execFind(function (err, data) {
    if (err)
      callback(err); // pass error along
    else {
      callback(null, [ data ]);
      // although I think you mean this (because 'data' is probably an array already)
      //   callback(null, data);
    }
  });

}, function(err, result) {
  if (err) return next(err);
  console.log("(it's empty): " + result); 
}); 

来源：https://stackoverflow.com/questions/19887995/async-node-js-data-flow-confusion