Concatenate data in Javascript functions

Question

I have two javascript functions.

This is one function and other one is also same.

function function1(.., .., callback){
    //database logic

 callback(data);

}

My requirement is to get data from both functions and send to client side.

function sendFunction(){

   function1(.., .., function(data1)){
      console.log(data1);
   }

   function2(.., .., function(data2)){
      console.log(data2);
   }

   sendToClient(data1+data2);
}

My issue is how can I take outside data1 and data2 from functions to concatenate. Guide me to achieve this task.

are you returning data1 and data2 from both the functions? — Aatif Bandey
– Aatif Bandey, Commented Sep 23, 2016 at 5:18
yes, console.log(data1) and console.log(data2) works fine. console.log(data1 + data2) returns empty. — Shashika
– Shashika, Commented Sep 23, 2016 at 5:25
returns empty means does it return undefined or anything else ? — Aatif Bandey
– Aatif Bandey, Commented Sep 23, 2016 at 5:27

felipeptcho · Accepted Answer · 2016-09-23 06:02:25Z

2

Considering that function1 and function2 are synchronous, you have to create two variables outside the functions to store the returned values.

function sendFunction () {
    var data1, data2;

    function1(.., .., function(d1) {
        data1 = d1;
        console.log(data1);
    });

    function2(.., .., function (d2) {
        data2 = d2;
        console.log(data2);
    });

    sendToClient(data1 + data2);
}

EDIT:

For async functions, I suggest you to use Promises:

function function1 () {
    return new Promise(function (resolve, reject) {
        // logic here

        // If everything is ok, call resolve().
        resolve("data1");

        // If something went wrong, call reject().
    });
}

function function2 () {
    return new Promise(function (resolve, reject) {
        // logic here

        // If everything is ok, call resolve().
        resolve("data2");

        // If something went wrong, call reject().
    });
}

function sendFunction () {
    Promise.all([function1(), function2()])
    .then(function (result) {
        sendToClient(result[0] + result[1]);
    })
    .catch(function () {
        console.log("The request failed. Try again.")
    });
}

sendFunction();

edited Sep 23, 2016 at 6:02

answered Sep 23, 2016 at 5:33

felipeptcho

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3 Comments

Bergi Over a year ago

With promises, you should just use Promise.all. Outer-scope variables are a horrible practice.

felipeptcho Over a year ago

@Bergi Fixed. I used to use jQuery's $.when(). I'm still getting used to JavaScript Promises. Thanks.

Bergi Over a year ago

Thanks, +1 :-) The updated version also has the benefit of running the two requests in parallel.

Jonas Wilms · Accepted Answer · 2016-09-23 05:46:55Z

0

Do sth like:

var datas=[];
var count=0;
function callback(data){
count++;
datas.push(data);
if(count==2){
//perfect both callbacks returned
proceedwith(datas);
}
}
function1(callback);
function2(callback);

If they are json objects, you cannot add them. Store them into an array, or inside of an object, or stringify them

edited Sep 23, 2016 at 5:46

answered Sep 23, 2016 at 5:32

Jonas Wilms

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1 Comment

Shashika Over a year ago

In here I intepreted what I need to do. You are correct. I need array to store two objects. but that is not the issue in here

Shashika · Accepted Answer · 2016-09-23 06:30:25Z

0

Finally, I found a way to do this.

function sendFunction () {      

    function1(.., .., function(data1) {
        console.log(data1);

        function2(.., .., function(data2) {
           console.log(data2);

            sendToClient(data1 + data2);
        });
    });


    sendToClient(data1 + data2);
}

edited Sep 23, 2016 at 6:30

answered Sep 23, 2016 at 6:06

Shashika

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2 Comments

felipeptcho Over a year ago

This is not a good way because it includes nesting. If you have more than 2 functions, it becomes complicated. Please, check my updated answer using the new JavaScript Promises.

Bergi Over a year ago

You don't need to use var data1, data2 and those assignments. Just go for function(data1) { and function(data2) { directly.

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