Null/undefined return in WordPress AJAX request

Question

I really need help on this one. I've been looking at it for hours and been getting nowehere. I am working with ajax in WordPress and this is kind of my first time doing so.

I have a function in my code that utlimately ends with the following:

echo json_encode($aData); 

I then have code in my js file written as follows:

 jQuery.ajax({
    url: "path/to/admin-ajax.php", //AJAX file 
    // dataType: 'json',
    type: 'POST',
    // contentType: 'application/json',     
    data: { action: "process_chart_data" },             
    success: function(chartData) {
        //Code, that need to be executed when data arrives after
        // successful AJAX request execution
        console.log("SUCCESS");         
        console.log(chartData);  

    }
});

You will notice the comments in the above code. When I view chartData in the console I get this:

{"title":"R=3+","dates":["06\/04\/2014","11\/05\/2014","15\/06\/2014","27\/07\/2014","17\/08\/2014","28\/09\/2014","05\/10\/2014","19\/10\/2014","09\/11\/2014","23\/11\/2014","14\/12\/2014"],"series":[{"data":[[1396738800000,284],[1399762800000,350],[1402786800000,212],[1406415600000,296],[1408230000000,220],[1411858800000,253],[1412463600000,200],[1413673200000,310],[1415491200000,180],[1416700800000,156],[1418515200000,290]],"name":"Bulls"}]}0

However when I uncomment the dataType and contentType this outputs a 0.

My issue is I am trying to access properties of the returned array such as chartData.title but all I get is 'undefined'.

I have looked at this from a few different approaches but after a few hours I have had to throw my hands up. I would be greatly appreciative for any assistance people might be able to provide here.

Answer 1

I am not sure the output you have provided is the correct one but do you notice the '0' character at the end of your string?

{"title":"R=3+","dates":["06\/04\/2014","11\/05\/2014","15\/06\/2014","27\/07\/2014","17\/08\/2014","28\/09\/2014","05\/10\/2014","19\/10\/2014","09\/11\/2014","23\/11\/2014","14\/12\/2014"],"series":[{"data":[[1396738800000,284],[1399762800000,350],[1402786800000,212],[1406415600000,296],[1408230000000,220],[1411858800000,253],[1412463600000,200],[1413673200000,310],[1415491200000,180],[1416700800000,156],[1418515200000,290]],"name":"Bulls"}]}0

That is enough to cause the JSON parser to fail.

Also, don't use the contentType property like that since you don't send any JSON, you should remove that line altogether.