How to use callback on $.post to get returned data (async function problem)

Question

I'd like to get true or false from $.post by calling abc(). I found this answer, but I don't get it to work.

Can someone give me a short example with my code?

function abc() {
    form = $('form');
    formData = form.serialize();

    $.post('file.php', formData, function(result) {
        form.each(function() {
            if (result === this.id) {
                return true;
                error = true;
            }
        });

        if (error === false) { // no error
            return true;
        }
    });
}

if (abc()) {
    // true // <- doesn't work, because $.post is an async function
}

Also `error = true;` will never be set because it is after a (useless) return — mplungjan, Feb 01 '20 at 15:42
You cannot call abc and test the result. Simply change your code so you move the code you had when true to a function you call when true — mplungjan, Feb 01 '20 at 15:45

score 0 · Answer 1 · answered Feb 01 '20 at 15:09

Have in mind that the response of the call to $.post is only available when the promise fulfills.

So, in order for the response to be available, you have to wait for the promise (as you do in abc in order to know what to return).

Having that in mind, you have to return the promise in abc in order to wait for its resolution:

function abc() {
    form = $('form');
    formData = form.serialize();

    // Note here we return the promise
    return $.post('file.php', formData, function(result) {
        if (result === 'abc') {
             return true;
        } else {
             return false;
        }
    });
}

// Now we wait for the promise to be resolved
abc().then(function(result) {
    if (result) {
        // Do your thing here!
    }
});

The problem now is, that result is always "true" because it shows me the returned data from php and not just true or false :/. — xif80599, Feb 01 '20 at 15:30

Nguyễn Văn Phong · Accepted Answer · 2020-02-01T15:44:24.267

0

You can achieve it by returning promise value, Then check it by using done method.

function abc() {
   form = $('form');
   formData = form.serialize();

   return $.post('file.php', formData);
}

abc().done(function(result){
    if(result === 'abc')
    // do something.
});

You can also use Callback function like this

function abc(mycalback) {
    form = $('form');
    formData = form.serialize();

    $.post('file.php', formData, mycalback);
}

function mycalback(response) {
    var result = false;
    form.each(function() {
            if (response=== this.id) {
                return true;
                result = true;
            }
        });
    return result;
}

edited Feb 01 '20 at 15:44

answered Feb 01 '20 at 15:10

Nguyễn Văn Phong

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Does this answer your question? Let me know if you need any help @xif80599 – Nguyễn Văn Phong Feb 01 '20 at 15:12
Isn't it possible to return just true or false from abc()? I've updated my code btw. :). – xif80599 Feb 01 '20 at 15:24
From my point of view, you should control value from `promise` value instead – Nguyễn Văn Phong Feb 01 '20 at 15:26
What about callbacks? [Here](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) is an example of a callback. Do you know how to use this in my case? – xif80599 Feb 01 '20 at 15:35
I've just updated my answer, please take a look @xif80599 . However, return boolean in your case does not make sense, So you need to do something as you wish instead of return true/false; – Nguyễn Văn Phong Feb 01 '20 at 15:50

How to use callback on $.post to get returned data (async function problem)

2 Answers2