Recursive Async Looping In Nodejs

I'm trying to do a recursive async loop to trace all the children of a particular object from a third-party lib in nodejs. Heres the pseudo code: var tracer = function(nodes){ va

Solution 1:

You must not push the recursive promises on the array in the delayed callback. Instead, you'll need to push a promise that represents the recursive results (resolves with those delayed produced promises) right away. Luckily, you even get exactly that back from that then call.

Additionally, I would swap out the each for a map, and do RSVP.all immediately inside the function, for not expecting the caller to deal with that.

functiontracer(nodes){
  var promises = nodes.map(function(node){
    // trace returns a promise ...var promise = builder.trace(node)
    var recusivePromise = promise.then(function(tree){
      // if we had children, get thoseif (tree.children.length)
        returntracer(tree.children));
      elsereturn node;// the leaf node itself
    });
    return recusivePromise; // which will resolve with the `tracer(…)` result// or the leaf
  });
  returnRSVP.all(promises);
}

tracer(myArr).then(function(allTrees){ … });

Solution 2:

I ended up going with a counter type approach ...

var traceDeps = function(parents, cb){
  var count = 0, 
    trees = [], 
    trace = function(nodes){
      nodes.forEach(function(node){
        count++;
        builder.trace(node).then(function(tree){
          trees.push(tree);

          if(tree.children.length){
            trace(tree.children);
          }

          count--;
          if (count === 0) cb(trees);
        });
      });
    };

  trace(parents);
};

traceDeps(myArr, function(trees){ ... });