Defining JSONP callback function

Question

I'm a bit new to JS and I'm having some problems with my code.

I have Ajax request to the server, from which I get the response. Since it's cross-domain request, I'm using JSONP.

$.ajax({
    url: "***",
    contentType: 'application/javascript',
    dataType: "jsonp",
    jsonpCallback: "parseResponse"
  })
    .done(function (response) {
        doSomething();
    })
    .fail(function (error)) {
        console.log(error);
  }

Response that I get:

parseResponse({...})

My problem is with understanding how parseResponse callback works. With this code I SOMETIMES get

"Uncaught ReferenceError: parseResponse is not defined" .

But part of responses get through OK (in .done function I filter response and from there, I fill a table).

How should be parseResponse defined correctly?

EDIT: "parseResponse" is default callback set by Geoserver service.

Example of response:

parseResponse({"type":"FeatureCollection","totalFeatures":"unknown","features":[],"crs":null})

Typically features property array would be filled with some data.

Answer 1

Remove jsonpCallback: "parseResponse" from your ajax call. That lets jQuery handle all the work for you. (It creates a unique function name, creates the function, passes the name to the endpoint, and cleans up the function when done.)

Also remove the contentType: "application/javascript" . You're not sending JavaScript code to the server.

$.ajax({
    url: "***", // <== Make sure this DOESN'T have ?callback= on it
    dataType: "jsonp"
})
.done(function(response) {
    doSomething();
})
.fail(function(error)) {
    console.log(error);
});

---

According to your comments, the target service (Geoserver) requires a ridiculous option for specifying the JSONP callback: format_options=callback:name . That doesn't play nicely with ajax at all (and I've never seen such obtuse support for JSONP before).

To handle it while not using a hardcoded name (because hardcoded names are a bad idea, you can't overlap calls), we have to play silly games like this:

var callbackName = "myJSONPCallback" + Date.now() + Math.floor(Math.random() * 100000);
$.ajax({
    url: "//the-url?format_options=callback:" + callbackName,
    // Include ----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    // in the URL
    dataType: "jsonp",
    jsonp: false,
    jsonpCallback: callbackName
})
.done(function(response) {
    doSomething();
})
.fail(function(error)) {
    console.log(error);
});

See ajax documentation (linked above) for details of the jsonp and jsonpCallback options.