Uncaught Syntax Error using JavaScript server side variable

Question

I'm working with Node.Js on server side, it generates a JSON, that I convert in an Object, and I need to access it from client side, in particular from a script in a HTML page.

EDIT: Server-side code

On the server side this is the code when the post request happens:

exports.plot = function(req, res){
    var json;
    request.post({
            uri:"http://127.0.0.1:8080/api/v1/datapoints/query",
            headers: {'Content-Type': 'application/json'},
            body:req.body.txt1
            },function (error, response, body) {
                if (!error && response.statusCode == 200) {

                    var json = JSON.parse(body); //JSON converted in an object
                    res.render('query', json);

                }
            }
        );

};

It was suggested me to use server side scripting (like the one used in ASP.NET) to access that object.

So I've used that syntax to get the values I want, however on the Chrome console I get this error "Uncaught SyntaxError: Unexpeted token (" .

Where I'm wrong?

Here's the code

<script>
 function(){
    var start = new Date();
        var queryLength = <%= queries.length %>, // This gives me a number correctly
        timestamps = [],
        tagsString = [],
        values = [],
        dataPoints = [];

        var metric = <%= queries[0].results[0].name %>; //Gives me correctly a string

    //il for che mi scorre tutta la risposta    
    for (var j = 0; j < queryLength; j++)
    {

    }
} 
</script>

the complete error is:

Uncaught SyntaxError: Unexpected token ( jquery-1.9.1.js:603
(anonymous function) jquery-1.9.1.js:603
jQuery.extend.globalEval jquery-1.9.1.js:604
jQuery.fn.extend.domManip jquery-1.9.1.js:6187
jQuery.fn.extend.append jquery-1.9.1.js:5949
(anonymous function) jquery-1.9.1.js:6074
jQuery.extend.access jquery-1.9.1.js:852
jQuery.fn.extend.html jquery-1.9.1.js:6038
(anonymous function) format-timestamp.js:36
fire jquery-1.9.1.js:1037
self.fireWith jquery-1.9.1.js:1148
done jquery-1.9.1.js:8074
callback jquery-1.9.1.js:8598

What kind of templating engine are you using? If you are not using a templating engine, then the html that gets sent to the broweser contains <%= queries.length %> and it is not surprising that there is a syntax error in your JS. — Andrew Eisenberg
– Andrew Eisenberg, Commented Jan 17, 2014 at 18:32
I don't think you've included the part of your JavaScript code that generates the error. What are you doing in the for loop? Do you have more JavaScript code to show? — AnalogWeapon
– AnalogWeapon, Commented Jan 17, 2014 at 18:34
@AndrewEisenberg what do you mean by templating engine? I use only Node.js at server side, now inside Nodeclipse because it's in developement — alessandrob
– alessandrob, Commented Jan 17, 2014 at 19:09
Then how does <%= queries.length %> get translated into html? — Andrew Eisenberg
– Andrew Eisenberg, Commented Jan 17, 2014 at 20:27

Guffa · Accepted Answer · 2014-01-17 21:44:40Z

2

That error has nothing to do with the JSON or the server side code.

The syntax error is here:

function(){

It looks like the beginning of a function expression, but you are not using it as an expression. It conflicts with the syntax of a function declaration, which would look something like this:

function functionName(){

The parser expects the name of the function to follow the function keyword, but instead there is a parenthesis.

If you want to declare a function, there should be a function name. If you want to use a function expression, then you need to use it as an expression, i.e.:

(function(){
  ...
})();

I added the () to actually call the function also, as it otherwise would just create the function and throw it away without calling it.

If you want to use the shorthand for the jQuery ready event, it looks like this:

$(function(){
  ...
});

Edit:

To recreate an object or an array in the Javascript code, you have to print it in the code in literal syntax. You can use JSON for this, as that is a subset of Javascript object syntax.

Pseudo code (I don't know what libraries node.js have for JSON):

var queries = <% toJson(queries) %>;

edited Jan 17, 2014 at 21:44

answered Jan 17, 2014 at 18:40

Guffa

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11 Comments

alessandrob Over a year ago

Thanks for your answer, anyway, as written in the other response, the problem should be related to the server side code, because once this is commented the error disappears. I tried also assigning a name to the function as you suggested, but nothing changes.

Guffa Over a year ago

@Markviduka: The code that you posted gives that syntax error, but it's possible that you have a similar error somewhere else in the code if changing it doesn't fix it or at least gives a different error message. There is an error in the server code though, but that should not cause a syntax error; there are string delimiters missing around the string value: var metric = "<%= queries[0].results[0].name %>";

alessandrob Over a year ago

For instance, if I write var query = <%= queries %>; alert ("Hello!"); the alert doesn't appear, if i comment variable query, it appears.

Guffa Over a year ago

@Markviduka: As the variable queries is an array in the server code, you would not get the script representation of it when you print it, you would get the string representation of it. Convert it to a JSON string if you want to put in in the code.

alessandrob Over a year ago

As you written, with delimiters the metric variable gives no errors, and the alert works. So if it's possible with a string, why it couldn't be possible with an object? Indeed, if I write var object = [<%= queries %>]; where queries is an object, the error returns.

|

Merlin · Accepted Answer · 2014-01-17 18:43:19Z

1

It looks like a jquery error.. I think the function(){} call is wrong you need $(function() {}); don't forget to add ); at the end.

Or if it's not the Jquery ready function that your are calling you have an syntax error and should do function myFunction(){}

try this

// replace `function(){}` width  `$(function() {});`
$(function() {
  var start = new Date();
        var queryLength = <%= queries.length %>, // This gives me a number correctly
        timestamps = [],
        tagsString = [],
        values = [],
        dataPoints = [];

        var metric = <%= queries[0].results[0].name %>; //Gives me correctly a string

    //il for che mi scorre tutta la risposta    
    for (var j = 0; j < queryLength; j++)
    {

    }
});

edited Jan 17, 2014 at 18:43

answered Jan 17, 2014 at 18:36

Merlin

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1 Comment

alessandrob Over a year ago

Thanks for the answer, anyway I've tried that syntax without the <%= %> code and it works properly. I don't think is a jQuery problem, or to be more precise, it won't be a standard jQuery problem, maybe it's related with the server side scripting (I use also Node.js)

AnalogWeapon · Accepted Answer · 2014-01-17 21:19:01Z

0

The problem is that the JavaScript in the browser isn't going to be able to understand the value of query as anything but a string. It doesn't matter if you output [1,2,3] or {"foo":"bar"}, the JavaScript is just going to interpret that as var query = "[1,2,3]" or var query = "{\"foo\":\"bar\"}".

As Guffa said in his comments: If you want to get the object in JavaScript you need to make sure ASP is outputting a valid JSON string representation of the object and then parse it in the JavaScript. So if your query object is {foo: bar} in ASP, you need to output the string "{\"foo\":\"bar\"}" from ASP. I don't know if ASP has any built in methods for this, but assuming it does (or you make one) and it's called toJSONString(): In your JavaScript, do:

var query = JSON.parse(<%= toJSONString(query) %>)

answered Jan 17, 2014 at 21:19

AnalogWeapon

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1 Comment

Guffa Over a year ago

Not at all, and that's not what I said. It works fine to output an object in JSON format directly in the code, i.e. pseudo code: <%= toJson(queries) %>. There is no need to convert it to JSON and put the JSON in a string in the code, and the parse the JSON. JSON is a subset of Javascript object syntax, so it works fine to use it as Javascript code.

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