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kali90

AJAX/JSON

in Using jQuery • 9 years ago

hi,

I can't get jQuery to parse the incoming JSON....

$('#btn_send_chat').click(function(e) {
e.preventDefault();
$.ajax({
type: "GET",
url: 'getChat.php',
// ?r_chat=1&last=' + lastMessage,
success: function(response) {
// handleReceiveChat();
$('#console').html( response );
$('#console').html( response.j_messages.j_message.length + ' == response.j_messages.j_message.length');
}
});

the JSON is created 'on the fly' in getChat.php... (last line in PHP is: echo $json; )

but the line

$('#console').html( response.j_messages.j_message.length + ' == response.j_messages.j_message.length');

throws error:

  response.j_messages.j_message is undefined...

I don't get this.. this line

$('#console').html( response );

returns:

{
"j_messages":{
"j_message":[{
"j_id":"0",
"j_user":"Admin",
"j_text":"You are not currently in a chat session. <a href=\"\">Enter a chat session here</a>",
"j_time":"05:21"
}
]
}
}

(not indented like this; this indent was done by JSON Lint....;-)

why then can't it parse response.j_messages.j_message???

thank you...

Replies(5)

kbwood.au

Re: AJAX/JSON

9 years ago

Try specifying the dataType as JSON:

$('#btn_send_chat').click(function(e) {
e.preventDefault();
$.ajax({
type: 'GET',
url: 'getChat.php',
dataType: 'json',
success: function(response) {
$('#console').html( response.j_messages.j_message.length +
' == response.j_messages.j_message.length');
}
});
});

Chrazy

Re: AJAX/JSON

9 years ago

As kbwood wrote, if you don't specify the dataType and you don't have the right content headers sent back with the data jQuery won't know how to handle it.

kali90

thank you for your response, kbwood... and thank you also Chrazy.... stupid question... oh brother...

I had thought it came in as JSON already, this is why I hadn't thought of it.. but of course what the PHP spits out is a string that just looks like a JSON, yes??

I also tried using parseJSON, but it returns null:

success: function(response) {
var objJSON = $.parseJSON(response);
// following throws error: objJSON is null...
$('#console').append(objJSON.j_messages.j_message[0].j_text);
.....
}

on a more general note, I had been confused about the many methods for ajax in jQuery, but just after I posted this question I found a handy reference:
http://net.tutsplus.com/tutorials/javascript-ajax/5-ways-to-make-ajax-calls-with-jquery/

I especially liked the list at the end that shows for what to use each method, and the table at the very end showing exactly what params you can pass to each method; do you agree with the info on this page?

thank you very much...

Kevin B

Re: AJAX/JSON

9 years ago

If you don't specify the dataType as json, jquery will interpret it as plain text, not json, since all json really is is plain text.

-- Kevin

Chrazy

Re: AJAX/JSON

9 years ago

My personal preference is to always use the ajax() method.
Not knowing PHP all that well, but the content header should probably be set as:

header('Content-type: application/json');

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