Node.js - Using the async lib - async.foreach with

问题:

I am using the node async lib - https://github.com/caolan/async#forEach and would like to iterate through an object and print out its index key. Once complete I would like execute a callback.

Here is what I have so far but the 'iterating done' is never seen:

    async.forEach(Object.keys(dataObj), function (err, callback){ 
        console.log('*****');

    }, function() {
        console.log('iterating done');
    });  

1. Why does the final function not get called?

2. How can I print the object index key?

回答1:

The final function does not get called because async.forEach requires that you call the callback function for every element.

Use something like this:

async.forEach(Object.keys(dataObj), function (item, callback){ 
    console.log(item); // print the key

    // tell async that that particular element of the iterator is done
    callback(); 

}, function(err) {
    console.log('iterating done');
});  

回答2:

async.each is very useful and powerful function which is provided by Async Lib .it have 3 fields 1-collection/array 2- iteration 3-callback the collection is referred to the array or collection of objects and iteration is refer to the each iteration and callback is optional . if we are giving callback then it will return the response or say result which you want to show you in the frontend

Applies the function iteratee to each item in coll, in parallel. The iteratee is called with an item from the list, and a callback for when it has finished. If the iteratee passes an error to its callback, the main callback (for the each function) is immediately called with the error.

Note, that since this function applies iteratee to each item in parallel, there is no guarantee that the iteratee functions will complete in order.

exapmle-

 var updateEventCredit = function ( userId, amount ,callback) {
    async.each(userId, function(id, next) {
    var incentiveData = new domain.incentive({
    user_id:userId,
        userName: id.userName,
        amount: id.totalJeeneePrice,
        description: id.description,
    schemeType:id.schemeType
    });

    incentiveData.save(function (err, result) {
        if (err) {
            next(err);
        } else {
                 domain.Events.findOneAndUpdate({
                    user_id: id.ids
                }, {
                    $inc: {
                        eventsCredit: id.totalJeeneePrice
                    }
                },{new:true}, function (err, result) {
                    if (err) {
                        Logger.info("Update status", err)
                        next(err);
                    } else {
                     Logger.info("Update status", result)
                     sendContributionNotification(id.ids,id.totalJeeneePrice);
                     next(null,null);       
                    }
                });
        }
    });