JSON.parse意外字符

Question

I have a JSON object stored in a mongoDB collection. The object represents the positions of 5 x images, 5 y images, and a tictactoe board image.

On an interval, I send a request to a php file that responds with this object, and then I want to parse that object and move the pieces accordingly.

this is my request:

$.getJSON
(
    "e4.php",
    "",
    function(data)
    {
        world = JSON.parse(data);
        moveObjects(world);
    }
);

but I get: JSON.parse: unexpected character

When I console.log data firebug gives me the right object so I know it's returning properly.

In e4.php:

$criteria = array("name" => "world");

$doc = $collection->findOne($criteria);

$conn->close();

print $doc['world'];

where conn is the connection, and collection is the collection I'm working in.

The database is updated in e3.php:

$encodedworld = $_REQUEST['data'];

$criteria = array("name" => "world");

$doc = $collection->findOne($criteria);

$doc['world'] = $encodedworld;

$collection->save($doc);

$conn->close();

print $encodedworld;

Any ideas? I'm stumped

Thanks in advance.

Answer 1

jQuery's getJSON deserializes the JSON for you, so data will be an object graph, not a string. From the documentation:

The success callback is passed the returned data, which is typically a JavaScript object or array as defined by the JSON structure and parsed using the $.parseJSON() method.

So since data has already been deserialized, you don't want or need to call JSON.parse on it. Doing so will implicitly call toString on data , which will return either [object Object] or [object Array] , hence JSON.parse not liking it as input. :-) Just use data directly:

$.getJSON
(
    "e4.php",
    "",
    function(world)         // <=== Changed name of argument
    {
        moveObjects(world); // <=== Used it directly
    }
);

---

Separately: Unless you declared world somewhere you didn't show, your code was also falling prey to The Horror of Implicit Globals . You probably wanted to have var in there. But with the change above, you don't need the variable at all, so...