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I have written a very simple test application that creates a websocket and parses the data it receives (server sends valid JSON data). The problem is that the first JSON object is parsed successfully, but all the subsequent objects are parsed with errors.

Here's all the code:

$("#connect").click(function ()
    {
        socket = new WebSocket("my server address");
        socket.onopen = function ()
        {
            $("#log").append("Connection opened.<br/>");

            socket.send(/* login information goes here */));
        };
        socket.onerror = function (e)
        {
            $("#log").append("Error: " + e.data + "<br/>");
        };
        socket.onclose = function ()
        {
            $("#log").append("Connection closed.<br/>");
        };
        socket.onmessage = function (e)
        {
            $("#log").append(index.toString() + ": " + e.data + "<br/><br/>");

            console.log("Parsing " + index);
            index++;
            var obj = JSON.parse(e.data);
            console.log("Parsed:");
            console.log(obj);
        };
    });

What I'm getting is: The first time "socket.onmessage" called - JSON is parsed and JS console displays an object. When second one arrives it outputs it to my "log", but JSON.parse fails with error "Uncaught SyntaxError: Unexpected token ILLEGAL". What is puzzling me is that the string that is received is a valid JSON object - I have tested it through several JSON validators. I have even copy-pasted it from my "log" put it in a separate file and parsed it with $.getJSON - and it worked fine, no errors.

Browser: Chrome 13.0.782.112

Any ideas would be helpful.

Thank you.

I have written a very simple test application that creates a websocket and parses the data it receives (server sends valid JSON data). The problem is that the first JSON object is parsed successfully, but all the subsequent objects are parsed with errors.

Here's all the code:

$("#connect").click(function ()
    {
        socket = new WebSocket("my server address");
        socket.onopen = function ()
        {
            $("#log").append("Connection opened.<br/>");

            socket.send(/* login information goes here */));
        };
        socket.onerror = function (e)
        {
            $("#log").append("Error: " + e.data + "<br/>");
        };
        socket.onclose = function ()
        {
            $("#log").append("Connection closed.<br/>");
        };
        socket.onmessage = function (e)
        {
            $("#log").append(index.toString() + ": " + e.data + "<br/><br/>");

            console.log("Parsing " + index);
            index++;
            var obj = JSON.parse(e.data);
            console.log("Parsed:");
            console.log(obj);
        };
    });

What I'm getting is: The first time "socket.onmessage" called - JSON is parsed and JS console displays an object. When second one arrives it outputs it to my "log", but JSON.parse fails with error "Uncaught SyntaxError: Unexpected token ILLEGAL". What is puzzling me is that the string that is received is a valid JSON object - I have tested it through several JSON validators. I have even copy-pasted it from my "log" put it in a separate file and parsed it with $.getJSON - and it worked fine, no errors.

Browser: Chrome 13.0.782.112

Any ideas would be helpful.

Thank you.

• javascript
• json
• websocket

Share Improve this question Follow asked Aug 19, 2011 at 1:30 stepanstepan 1,10522 gold badges88 silver badges1414 bronze badges 5

• 1 maybe you've already set the content type in your server? then the data does not need any more parsing. already happened to me, went nuts for a day for nothing – pif Commented Aug 19, 2011 at 1:47
• @pif hmm, I don't think that is the case here, the data is received via websocket. – stepan Commented Aug 19, 2011 at 2:01
• ahh ok... in my case anyway i'm using java servlets, then set the {response.setContentType("application/json")} and then tried to parse that like what you're doing and got Unexpexted token error thingy. like you i tried to copy and paste what browser is getting and it also is a valid json. when i tried NOT to parse it and access the data, works like a charm. – pif Commented Aug 19, 2011 at 2:27
• Have you tried just spitting out the output from 'e.data' (both first and second attempts) and paring them, possibly post them here. – Sunday Ironfoot Commented Aug 19, 2011 at 16:06
• @Sunday I have tried that. And I do believe it is a bug, since the solution to this problem was to use JSON.parse source code instead of actually calling JSON.parse. You can take a look at "2nd Update" here - stackoverflow./questions/7123908/… – stepan Commented Aug 21, 2011 at 14:32

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 3

ES5 spec http://ecma262-5./ELS5_HTML.htm#Section_15.12.1 defines JSON whitespace as tab, cr, lf or sp. The Crockford skip-space uses the following code :

        white = function () {

// Skip whitespace.

            while (ch && ch <= ' ') {
                next();
            }
        },

So if you have any spurious null characters or form-feeds etc in your response then the ES5 JSON parse will throw an error while the Crockford version will not.

You should do:

$.parseJSON( json );

see this for more info: http://api.jquery./jQuery.parseJSON/

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