Can't parse XMLHttpRequest.response to Object or Array - php

Question

I'm trying to refresh the content of my cells of an table. Therefore, I have a JavaScript which contains an AJAX request to a .php file, which creates my content that I want to insert into my table via JavaScript. The .php files last command is something like echo json_encode($result);.
Back in the JavaScript it says:
var testarray = xmlhttp.response;
alert(testarray);
But the outut from the alert looks like:
{"1":{"1":"3","2":"0","3":"2","4":"0"}}{"1":{"1":"3","2":"0","3":"2","4":"0"},"2":{"1":"2","2":"1","3":"1","4":"1"}}...
So it seems the variable testarray isn't handled as an array but as a string. I already tried var testarray = JSON.parse(xmlhttp.response), but this doesn’t work. Neither does eval() works.
I don't know what to do, so the response of my request becomes an object.

Answer 1

There are 2 strange things in your json:
this part is not json valid: ...}{...
two object should be separated by comas
The notation is object with string indexes not array with int indexes
it should be something like: [[1,2,3,4],[5,6,7,8]]
for the point 1. it looks like you have a loop that concatenate many json
for the point 2. the object notation can be used as an array so it doesn't matter
Some code:
//the folowing code doesn't work: }{ is not parsable
var a=JSON.parse('{"1":{"1":"3","2":"0","3":"2","4":"0"}}{"1":{"1":"3","2":"0","3":"2","4":"0"},"2":{"1":"2","2":"1","3":"1","4":"1"}}');
//the folowing code work and the object can be used as an array
var a=JSON.parse('{"1":{"1":"3","2":"0","3":"2","4":"0"},"2":{"1":"2","2":"1","3":"1","4":"1"}}');
alert(JSON.stringify(a[1]));
//the folowing code displays the real notation of a javascript array:
alert(JSON.stringify([1,2,3,4]));

Answer 2

I think that the problem here might be that your arrays do not have index 0.
e.g. if you output this from the server - it would produce an object:
$result = [];
for ($i = 1; $i < 5; $i++) $result[$i] = $i;
echo json_encode($result); // outputs an object
if you output this from the server - it would produce an array:
$result = [];
for ($i = 0; $i < 5; $i++) $result[$i] = $i;
echo json_encode($result); // produces an array
Anyways, even if your server outputs array as object - you should still be able to access it normally in javascript:
var resp = xmlhttp.responseText, // "responseText" - if you're using native js XHR
arr = JSON.parse(resp); // should give you an object
console.log(arr[1]); // should give you the first element of that object