CODEWITHSUNDEEP
javascriptnode.jsasynchronous
Mahesh Singh Chouhan
Mahesh Singh Chouhan

Reputation: 2588

How to make it async in javascript or node?

var responseArr = new Array();
async.each(response, function (value, k) {
    if(isDateFlag)
    {
         var defaultValue = value.auction_id;
         grpArray.push(value.title);
         var postData = {
             parent_id : parent_id,
             defaultValue : defaultValue,
             isDateFlag : isDateFlag,
             search_text : search_text
         }
         getChildNotificationList(postData, function (childArrayData) {
            //Creating the response array

             responseArr.push({
                'notification_id' : childArrayData['notification_id'], 
                'notification_text' : childArrayData['notification_text']
             });
        });

     }
});

return responseArr;//Blank Array

I want to return the final responseArr after manipulating it from child data query. It return blank array because it does not wait for the query response.

So how it can be async. Thanks

Upvotes: 2

Views: 84

Answers (1)

Madhukar
Madhukar

Reputation: 196

I referred http://justinklemm.com/node-js-async-tutorial/ and https://github.com/caolan/async.

This happens because the control goes on executing the code since javascript is synchronous. For getting the expected result modify the code as below:

var responseArr = new Array();
async.each(response, function (value, k) {
  if(isDateFlag){
    var defaultValue = value.auction_id;
    grpArray.push(value.title);
    var postData = {
      parent_id : parent_id,
      defaultValue : defaultValue,
      isDateFlag : isDateFlag,
      search_text : search_text
    }
    getChildNotificationList(postData, function (childArrayData) {
      //Creating the response array

      responseArr.push({
        'notification_id' : childArrayData['notification_id'], 
        'notification_text' : childArrayData['notification_text']
      });
      k();
    });
  } else {
    k();
  }
}, function (err) {
  if (err) {
    console.log(err);
  } else {
    return responseArr;
  }
});

The above code is inside a function block. You could get the result by calling the function.

Including the answer using async.map:

async.map(response, function (value, k) {
  if(isDateFlag){
    var defaultValue = value.auction_id;
    grpArray.push(value.title);
    var postData = {
      parent_id : parent_id,
      defaultValue : defaultValue,
      isDateFlag : isDateFlag,
      search_text : search_text
    }
    getChildNotificationList(postData, function (childArrayData) {

      k(null, {
        'notification_id' : childArrayData['notification_id'], 
        'notification_text' : childArrayData['notification_text']
      });
    });
  } else {
    k(null, {
      'notification_id' : '', 
      'notification_text' : ''
    });
  }
}, function(err, results){
  // results is now an array
  return results;
});

Upvotes: 3

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