"undefined" after passing JSON array via AJAX

Asked Aug 10 '18 at 12:19

Active Aug 10 '18 at 12:20

Viewed 37 times

With the use of this answer I appear to have got the passing of an array from one PHP file to another working with AJAX Javascript.

However, if I try to use the data at all, it comes back as "undefined".

Am I missing a step?

ajax.php:

<?php
  $letters = array('A','B','C');
  echo json_encode($letters);
?>

JS:

function loadDoc() {
        letters = new Array();
        $.ajax({
                url:"ajax.php",
                type:"POST",
                success:function(msg){
                        letters = msg;
                },
                dataType:"json"
        });
        document.getElementById("demo").innerHTML = letters[0];
  }

Ultimately I just want to have the array back in the format ['A', 'B', 'C'] for use with chart.js.

asked Aug 10 '18 at 12:19

chivs688

You can use a callback function – Mihai Alexandru-Ionut Aug 10 '18 at 12:20
Move the `innerHTML` assignment inside success callback. You can't eat a pizza before it gets delivered. Also set dataType – charlietfl Aug 10 '18 at 12:22
How would I go about doing that? – chivs688 Aug 10 '18 at 12:23
Cut and paste it – charlietfl Aug 10 '18 at 12:23
@charlietfl Moving it inside worked thanks. Is the dataType not set with the dataType:"json" I have there? And also, is the letters array now in the format ['A', 'B', 'C']? Or do I need to convert it to that? – chivs688 Aug 10 '18 at 12:27
Oh yes it is (dataType)...am so used to seeing it above success I missed it. No worries there – charlietfl Aug 10 '18 at 12:38
The dataType;json means you have an array parsed from json inside the success already. That array can be any nested structure you want – charlietfl Aug 10 '18 at 12:39
@charlietfl Perfect thank you so much! – chivs688 Aug 10 '18 at 12:51
@charlietfl Is it possible to pass two arrays through at the same time? All working perfectly with one but if I try and pass a second one in the same way in same function it fails ? – chivs688 Aug 10 '18 at 13:16
Only if they are nested in an outer object. Can only do one `echo json_encode($output)` – charlietfl Aug 10 '18 at 13:24
@charlietfl Created an array of the two arrays and sent that over, worked perfectly. – chivs688 Aug 10 '18 at 13:51

"undefined" after passing JSON array via AJAX

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