Uncaught SyntaxError: Unexpected token :

Question

I am running an AJAX call in my MooTools script, this works fine in Firefox but in Chrome I am getting a Uncaught SyntaxError: Unexpected token : error, I cannot determine why. Commenting out code to determine where the bad code is yields nothing, I am thinking it may be a problem with the JSON being returned. Checking in the console I see the JSON returned is this:

{"votes":47,"totalvotes":90}

I don't see any problems with it, why would this error occur?

vote.each(function(e){
  e.set('send', {
    onRequest : function(){
      spinner.show();
    },
    onComplete : function(){
      spinner.hide();
    },
    onSuccess : function(resp){
      var j = JSON.decode(resp);
      if (!j) return false;
      var restaurant = e.getParent('.restaurant');
      restaurant.getElements('.votes')[0].set('html', j.votes + " vote(s)");
      $$('#restaurants .restaurant').pop().set('html', "Total Votes: " + j.totalvotes);
      buildRestaurantGraphs();
    }
  });

  e.addEvent('submit', function(e){
    e.stop();
    this.send();
  });
});

Answer 1

This has just happened to me, and the reason was none of the reasons above. I was using the jQuery command getJSON and adding callback=? to use JSONP (as I needed to go cross-domain), and returning the JSON code {"foo":"bar"} and getting the error.

This is because I should have included the callback data, something like jQuery17209314005577471107_1335958194322({"foo":"bar"})

Here is the PHP code I used to achieve this, which degrades if JSON (without a callback) is used:

$ret['foo'] = "bar";
finish();

function finish() {
    header("content-type:application/json");
    if ($_GET['callback']) {
        print $_GET['callback']."(";
    }
    print json_encode($GLOBALS['ret']);
    if ($_GET['callback']) {
        print ")";
    }
    exit; 
}

Hopefully that will help someone in the future.

Answer 2

I did Wrong in this

   `var  fs = require('fs');
    var fs.writeFileSync(file, configJSON);`

Already I intialized the fs variable.But again i put var in the second line.This one also gives that kind of error...

Answer 3

I had the same problem and it turned out that the Json returned from the server wasn't valid Json-P. If you don't use the call as a crossdomain call use regular Json.

Answer 4

For me the light bulb went on when I viewed the source to the page inside the Chrome browser. I had an extra bracket in an if statement. You'll immediately see the red circle with a cross in it on the failing line. It's a rather unhelpful error message, because the the Uncaught Syntax Error: Unexpected token makes no reference to a line number when it first appears in the console of Chrome.

Answer 5

This happened to me today as well. I was using EF and returning an Entity in response to an AJAX call. The virtual properties on my entity was causing a cyclical dependency error that was not being detected on the server. By adding the [ScriptIgnore] attribute on the virtual properties, the problem was fixed.

Instead of using the ScriptIgnore attribute, it would probably be better to just return a DTO.

Answer 6

"Uncaught SyntaxError: Unexpected token" error appearance when your data return wrong json format, in some case, you don't know you got wrong json format.
please check it with alert(); function

onSuccess : function(resp){  
   alert(resp);  
}

your message received should be: {"firstName":"John", "lastName":"Doe"}
and then you can use code below

onSuccess : function(resp){  
   var j = JSON.decode(resp); // but in my case i'm using: JSON.parse(resp); 
}

with out error "Uncaught SyntaxError: Unexpected token"
but if you get wrong json format
ex:

...{"firstName":"John", "lastName":"Doe"}

or

Undefined variable: errCapt in .... on line<b>65</b><br/>{"firstName":"John", "lastName":"Doe"}

so that you got wrong json format, please fix it before you JSON.decode or JSON.parse