CODEWITHSUNDEEP
javascriptnode.jsexpresscallbackpromise
RetroCode
RetroCode

Reputation: 332

Async issue on nodejs POST request

I am trying to apply a custom function inside a Post Request, but it returns undefined.

I know that this is some kind of async issue, I just cant figure out what might be the problem.

Chunk of code where problem resides

console.log(text); // <---- This shows correct value
A.prepare(function (text) { 
    console.log(text) // <---- This shows undefined
    B.write(text, function (response) {
        sendTextMessage(sender,response.message)
        return response.message;
    });
});

Whole code

app.post('/webhook/', function (req, res) {
    // addPersistentMenu();
    let messaging_events = req.body.entry[0].messaging;
    for (let i = 0; i < messaging_events.length; i++) {
        let event = req.body.entry[0].messaging[i];
        let sender = event.sender.id;
        if (event.message && event.message.text) {
            let text = event.message.text;
            console.log(text);
            A.prepare(function (text) {
                B.write(text, function (response) {
                    sendTextMessage(sender,response.message)
                    return response.message;
                });
            });   
        }
        if (event.postback) {
            let text = JSON.stringify(event.postback);
            sendTextMessage(sender, "Postback received: "+text.substring(0, 200));
            continue;
        }
    }
    res.sendStatus(200)
});

Upvotes: 0

Views: 103

Answers (2)

abdulbari
abdulbari

Reputation: 6232

Update

You are getting text value as undefined since you are accessing it in a callback function. And you have also given text parameter in the callback function. And Priority always goes to local that means every time you'll get the local value of text which is undefined now. you must change one of those variable names.

As I have changed text to text1 now you can get text1 value in callback function

And if you want to pass variable in A.prepare() function, you can add multiple parameters on basis of requirement.

like this:

A.prepare(param1,param2,param3,...,function(text){
    //Do your stuff
})

Here is you updated code: 

app.post('/webhook/', function(req, res) {
    //  addPersistentMenu();
    let messaging_events = req.body.entry[0].messaging;
    for (let i = 0; i < messaging_events.length; i++) {
        let event = req.body.entry[0].messaging[i];
        let sender = event.sender.id;
        if (event.message && event.message.text) {
            let text1 = event.message.text;
            console.log(text1);
            A.prepare(function(text) {
                B.write(text1, function(response) {
                    sendTextMessage(sender, response.message)
                    return response.message;
                });
            });


        }
        if (event.postback) {
            let text = JSON.stringify(event.postback);
            sendTextMessage(sender, "Postback received: " + text.substring(0, 200));
            continue;
        }
    }
    res.sendStatus(200)
});

Upvotes: 1

Dario
Dario

Reputation: 6280

It's a scope issue, not an async one.

In the line

A.prepare(function (text) {

text is actually the parameter passed to the function and used internally to the function itself. It does not refer to text you are logging in the line above.

Upvotes: 1

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