Asynchronously tree traversal using tree-model-js

Question

May I know is there a way to walk/traverse tree asynchronously using tree-model-js. There is a walk function in tree-model-js. However, it seems it is not an aync function.

Basically, I have some aync processes to process each node of the tree. I need a way to aync traverse the data tree to make sure every aync process happened in certain order (eg: pre-order) and return the final result using a callback upon finish traversing the tree.

If tree-model-js don't have such function, is there a way to traverse my datatree asynchronously ?

Answer 1

tree-model-js does not support async traversal. But, you can still compose or call your async code for each visited node.

If I understood your question correctly, you need to wait for the parent long task to finish before calling the child long task. This might help you:

var tree = new TreeModel();

var root = tree.parse({
    id: 1,
    children: [
        {
            id: 11,
            children: [{id: 111}]
        },
        {
            id: 12,
            children: [{id: 121}, {id: 122}]
        },
        {
            id: 13
        }
    ]
});

function longTask(node) {
  // Some long running task
  console.log("Running long task on node " + node.model.id);

  // Fake result
  return "res=" + node.model.id;
}

function asyncWalk(node) {
  var leafPromises = [];
  var promisesTemp = {};

  node.walk(function (node) {
    var nodePromise;
    if (node.isRoot()) {
      nodePromise = Q.fcall(function () {
        return [longTask(node)];
      });
    } else {
      nodePromise = promisesTemp[node.parent.model.id].then(function (prevResult) {
        return prevResult.concat(longTask(node));
      });
    }

    if (!node.hasChildren()) {
      leafPromises.push(nodePromise);
    } else {
      promisesTemp[node.model.id] = nodePromise;
    }
  });

  return Q.all(leafPromises);
}

// Using our async walk function...
asyncWalk(root).then(function (leafPromisesResult) {
  leafPromisesResult.forEach(function (leafPromiseResult) {
    console.log("ordered results: " + leafPromiseResult);
  });
});

Note the asyncWalk function composes a promise for each path from root to leaf and then executes each of these composed promises concurrently. I've used the Q library for promises because I'm familiar with it.

Not sure if this helps with your use-case. You can play with this code here.