How to access an object created within a function from another function

Question

I'm new to JavaScript and NodeJS, and I need to solve this issue quickly.

      connection(getSQL2)
    .then((table)=> {
        table.forEach(row=> {
            let obj = {
                countryid: row.IdPais,
                country: row.NombrePais
            };
            data.push(obj);
          });

        });

console.log(obj);

When I try to display the object using console.log, I get undefined, which seems pretty obvious. But what would be an easy way to get it to display the Object 'obj' that was created above?

UPDATE: Just to clarify, console.log is used here only as an example. I need to access the object from outside that function however I can.

Thanks in advance!

Move the console.log call inside the callback, where you defined `obj`. — Felix Kling, Dec 18 '16 at 06:40
I just put the console.log outside to make it clear that I need to access the object from outside. I need to get some data from that object within some other function. As if it was a global variable. Thanks anyway. — David Martínez, Dec 18 '16 at 06:47
*"I need to access the object from outside that function however I can."* And that's usually a mistake. Why do you think you need to do that? Please provide a complete example. Please read [Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference](http://stackoverflow.com/q/23667086/218196). — Felix Kling, Dec 18 '16 at 08:39
I'm working on a project where we need to dynamically migrate an entire MsSQL db and put the contents of each table into a different MongoDB collection. — David Martínez, Dec 18 '16 at 08:49
In this particular case I need to merge two SQL tables into a single Mongo collection. I know how to get fields from an object. But I can't access it because it's not a global variable. — David Martínez, Dec 18 '16 at 08:50
*"I can't access it because it's not a global variable."* You don't need global variables. Put the code that needs access to the data into a function. Call the function from the callback and pass the data to it. — Felix Kling, Dec 19 '16 at 07:35

Mike · Answer 1 · 2016-12-18T06:51:40.420

0

Two things going on here.

1) You're using a promise and promises asynchronously resolve. Good rule of thumb is any code that ends with .then(...) is going to be a promise. What that means is that code underneath it can execute before the promise is finished and if it reads those values before the promise has finished resolving they will be read as undefined.

2) You use the let keyword to define your variable which means it will only be defined in the scope:

row => {
            let obj = {
                countryid: row.IdPais,
                country: row.NombrePais
            };
            data.push(obj);

            // Show the object where it is defined
            console.log(obj);
          }

edited Dec 18 '16 at 06:51

answered Dec 18 '16 at 06:41

Mike

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In that case it works, but console.log is not precisely what I need. I need to access the object as if it were a global variable from another function. Thanks anyway. – David Martínez Dec 18 '16 at 06:45
Don't you have access to it in your `data` array? – Mike Dec 18 '16 at 06:52
Only inside the arrow function. – David Martínez Dec 18 '16 at 06:58

score 0 · Answer 2 · edited Dec 18 '16 at 08:20

0

You need to do this:-

 async database()
{

      try {
            const table= await connection(getSQL2);
            if (table!== null)
            {
             table.forEach(row=> {
              let obj = {
                          countryid: row.IdPais,
                          country: row.NombrePais
                        }; 
             console.log('This will resolve the promise',obj);
            }
            else 
            {
             //anything needed 
            }
          } 
            catch (error) 
           {
                       // Error retrieving data
           }
}

async and await are the keywords used in parallel. await keyword will not allow the control to go down until data is fetched.

edited Dec 18 '16 at 08:20

Ravi Shankar Bharti

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answered Dec 18 '16 at 07:14

Codesingh

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Thank you for your answer. I think this one would be the right path. But I'm getting this: async database() { ^^^^^^^^ SyntaxError: Unexpected identifier – David Martínez Dec 18 '16 at 07:24
I have tried this approach my issues were solved and its the correct way to resolve the promise. are you using this function in node? – Codesingh Dec 18 '16 at 08:03
I'm using Node 7.1.0 to import some SQL tables into MongoDB collections. – David Martínez Dec 18 '16 at 08:09
remove async and await keywords and then try. – Codesingh Dec 18 '16 at 08:13
you can make obj as a global variable and you can use it anywhere – Codesingh Dec 18 '16 at 08:19
function database() { try { const table = connection(getSQL2); if (table!== null) { table.forEach(row=> { let obj = { countryid: row.IdPais, country: row.NombrePais }; console.log('This will resolve the promise',obj); }) } else { //anything needed } } catch (error) { // Error retrieving data } } – David Martínez Dec 18 '16 at 08:21
Now there's no output at all. It just runs and closes without issues. – David Martínez Dec 18 '16 at 08:23
put console in else – Codesingh Dec 18 '16 at 08:24
if its going to else then we have to use async and await keywords – Codesingh Dec 18 '16 at 08:25
TypeError: table.forEach is not a function at database – David Martínez Dec 18 '16 at 08:26
You need to use async and await – Codesingh Dec 18 '16 at 08:36
Use babel to run async and await – Codesingh Dec 18 '16 at 08:38
how did you call the function? – Codesingh Dec 18 '16 at 08:38
I called it database(); – David Martínez Dec 18 '16 at 08:58
try calling new database() – Codesingh Dec 18 '16 at 09:59
If it doesn't work then there is a problem of usage of async keyword in node es7. you have to use babel to access these keywords. Don't worry I will tell you how to work around it. – Codesingh Dec 18 '16 at 10:01

Ravi Shankar Bharti · Answer 3 · 2016-12-18T07:51:30.067

0

you can create a global variable, and assign the value to that variable inside the that function.

Then, you will be able to access the variable obj outside the function also.

var temp;//declare a global variable here.
connection(getSQL2)
.then((table)=> {
    table.forEach(row=> {
        let obj = {
            countryid: row.IdPais,
            country: row.NombrePais
        };
        data.push(obj);
        temp = obj;//assign value to global variable here
      });

    });

console.log(temp);//you can access the 'obj' using temp

Hope this helps you.

edited Dec 18 '16 at 07:51

answered Dec 18 '16 at 07:25

Ravi Shankar Bharti

8,922
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Sadly not. Still undefined. – David Martínez Dec 18 '16 at 07:39
sorry, you need to do `console.log(temp)` , i will edit my answer. – Ravi Shankar Bharti Dec 18 '16 at 07:51

How to access an object created within a function from another function

3 Answers3