- From: <nmork_consultant@cusa.canon.com>
- Date: Mon, 4 Aug 2014 11:36:19 -0400
- To: David Bruant <bruant.d@gmail.com>
- Cc: Austin William Wright <aaa@bzfx.net>, Glenn Maynard <glenn@zewt.org>, "Tab Atkins Jr." <jackalmage@gmail.com>, public-webapps <public-webapps@w3.org>
- Message-ID: <OF606B71B0.7A5A4653-ON85257D2A.00547018-88257D2A.0055B906@cusa.canon.com>
I've seen that sort of code before. Sometimes unforseen events occur leaving you with a nonworkable screen. I tend to trust Javascript less than the environment on the server. Yes, there are better ways to build a DB application than web technology, but we are presented with the programming challenge of adding to a portion of DB application to an existing intranet application and now need the tools that will make the browser behave very non-web for a few moments. Can be a challenge. I still don't understand how this request has become a harangue to make sure I know that everybody thinks I am wrong to make such a request. I spoke about specific situations where I found synchronous xmlhttprequests to be useful and based on that, I expect them to be useful in the future. What I get back are very general vague assertions that seem to 1. Assume I never use asynchronous xmlhttprequests (not true, I use them predominantly) 2. Seem to ask me to take into account all situations, imagine all possibilities when I am only trying to solve 1 issue on 1 screen in 1 application My only assertion is: when synchronous xmlhttprequests are required, async WILL NOT WORK and are not appropriate. Simply repeating the mantra over and over is not convincing. From: David Bruant <bruant.d@gmail.com> To: nmork_consultant@cusa.canon.com, Cc: Austin William Wright <aaa@bzfx.net>, Glenn Maynard <glenn@zewt.org>, "Tab Atkins Jr." <jackalmage@gmail.com>, public-webapps <public-webapps@w3.org> Date: 08/04/2014 08:07 AM Subject: Re: =[xhr] Le 04/08/2014 15:30, nmork_consultant@cusa.canon.com a écrit : This is an intranet application. The server is in the next room (locked, of course.) I was seeing this one coming when I wrote my paragraph :-p If you're in a tightly controlled environment, one could question the choice of a web application, but that's beyond the point of this email. However, many (not all) POST operations require only 1 channel to be active at a time, especially in intranet applications. As someone else noted, how do you know two computers aren't connected at the same time? Or even that the same user isn't logged in in two different machines within the network? Note also that as others said, sync xhr doesn't freeze the browser, so if your application isn't robust to the user changing tab, or going back, you may have a bug you want to fix. If your answer resembles even vaguely "because I control the environment and want to prevent the user from doing x, y, z and will as long as I can", then, I'd like to question again whether you really want to make your intranet application run a web browser. There are lots of other choices to make non-web applications, but the web platform took the path of prioritizing the end-user concerns above all else. See the "Priority of Constituencies" : http://www.w3.org/TR/html-design-principles/#priority-of-constituencies We've had a foggy period at the beginning of the web, but it's clear now that end-users are considered as a priority in web standards and implementors (though obviously various parties will see end-user interests from a different perspective). If you care about how your software ensures some guarantees for your database above providing a good user experience, the web might not be where you want to make your application and I think that you will keep meeting resistance in web standards mailing-lists. No user wants to be given the freedom to accidentally screw up. Why would you write code that provides that freedom, though? In cases like you describe, I would send the POST request asynchronously and then disable any user interface that allows to send another request until the server comes back with a 200 (or equivalent) via either removing the event listeners. In essence, that would look like: var postUrl = '...'; postButton.addEventListener('click', function clickHandler(){ var xhr = new XMLHttpRequest(); xhr.open('POST', postUrl); xhr.addEventListener('load', function(){ // POST came back, re-enable the button postButton.removeEventListener('click', clickHandler); postButton.setAttribute('disabled', 'disabled'); }); xhr.send(); // disable UI for POSTing postButton.removeEventListener('click', clickHandler); postButton.setAttribute('disabled', 'disabled'); // maybe add a spinner somewhere and/or invite the user // to have a hot beverage of their choice as you suggested }); Of course, disable any other UI element you need, error handling is missing, etc, but you get the idea. The above code demonstrates that you can prevent the user from further interacting with the database, yet use async xhr. David
Received on Monday, 4 August 2014 15:36:57 UTC