jsonp comet hanging request causes ugly “loading” status on browsers

I'm using jsonp to do cross-domain comet requests, and the "loading" status is really annoying.

Is there any way to suppress this with javascript?

For those who are unfamiliar with jsonp, it basically injects a script tag, except in my case, I'm hanging the request on my server without returning the request until a later time.

During this time, browsers see my request as a "loading" state.

I am using this: http://code.google.com/p/jquery-jsonp/

Thanks in advance!

Answers:

Answer

As far as I know, there is no way to suppress the loading status using Javascript, regardless of why you have it.

However, there is at least one alternative for cross-domain COMET which wouldn't trigger the loading status in the first place. XMLHttpRequest doesn't set the loading status and, according to my tests, the CORS (Cross-Origin Resource Sharing) spec which allows cross-domain XHR is pretty well supported.

Basically, support is as follows: (According to a mix of browser documentation and my own tests for a project I'm working on)

Full support in:

  • Gecko 1.9.1+ (Firefox 3.5, SeaMonkey 2.0, etc. Tested good Firefox 3.6.8 and SeaMonkey 2.0.7)
  • WebKit (Safari 4+, Chrome 3+, etc.. Tested working on Safari 4 on OSX, Safari 5 on WinXP, Chrome 5.0.375.127 (Stable channel), Midori 0.2.7, the new Flock, Epiphany 2.30.2, luakit, and uzbl)

Untested, but should be fully supported:

  • Fluid (WebKit-based MacOS alternative to Mozilla Prism and Chrome's "Create Application Shortcuts...")

Limited support in:

  • Internet Explorer 8 (Microsoft implemented an XDomainRequest() object instead and, using security as an excuse, didn't implement the flag to pass credentials and cookies with the request)
  • Sleipnir (Support is determined by which version of MSHTML it's embedding)

Notably unsupported:

  • Opera (As of 11.01.1190, no support whatsoever)
  • Camino (As of 2.0.5, still based on Gecko 1.9.0 (Firefox 3.0))
  • Arora (As of 0.10.2, inherits WebKit's CORS API but has a bug that causes requests to fail)
  • old, Mozilla-based Flock (Based on Gecko 1.9.0 (Firefox 3.0))

It's not a complete list, but it's every browser with userscript support I could find to test. I've already taken the time to cite my sources on the CORS wikipedia page if you want them.

The simplest solution I can think of would be to test for CORS and then fall back to JSONP so that people using a modern browser get a perfect experience and people using something older see the loading status as an unavoidable side-effect.

Here's the MDC page on how CORS works.

Answer

If you begin your first request after the page has finished loading, you should be able to avoid the loading indicator.

$(function () {
    setTimeout(function () {
        $.jsonp(...)
    }, 1000);
});

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