jsonp comet hanging request causes ugly “loading”

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!

回答1:

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.

回答2:

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);
});