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IMHO, no modern JS developer should ever need to create a blocking alert or prompt; the reason the native alert or prompt functions block is because, well, they

by Mahn 14y ago

IMHO, no modern JS developer should ever need to create a blocking alert or prompt; the reason the native alert or prompt functions block is because, well, they are not designed for what the web is today.

JoeCortopassi 14y ago
Just out of curiosity, if you had a web app like Gmail, and your user accidentally went to close their browser window with an unsaved email half done, how would you plan on warning them without blocking events?
- svachalek 14y ago
  Save it in drafts and notify them when they come back.
  - JoeCortopassi 14y ago
    So Facebook and Twitter should also save drafts of posts you were going to make? What if latency is non-trivial, or connection is lost? Do I also want to send ajax posts for drafts every second to ensure that as little as possible is lost? A lot of this is mitigated by a very simple confirm("Are you sure you want to leave?");
    - kevincennis 14y ago
      Twitter actually does save drafts in localStorage.
    - ianstormtaylor 14y ago
      Yeah but for all the times when I really do want to leave, now I have to annoyingly click "Yes" in a dialog I didn't expect in the first place. I like the localStorage solution for drafts much better.
- teraflop 14y ago
  You use the onbeforeunload event, which doesn't block the event thread. (EDIT: actually it does, just not while JS code is executing, unlike alert().) In fact, the HTML5 spec permits browsers to disregard the normal blocking behavior of alert()/confirm()/prompt() (making them no-ops) while this event is being handled: https://developer.mozilla.org/en-US/docs/DOM/window.onbeforeunloadwhile https://developer.mozilla.org/en-US/docs/DOM/window.onbefore... the dialog box is open
  - teraflop 14y ago
    I managed to break that link somehow and can no longer edit it, here's the correct one: https://developer.mozilla.org/en-US/docs/DOM/window.onbeforeunload https://developer.mozilla.org/en-US/docs/DOM/window.onbefore...

by Mahn 14y ago

JoeCortopassi 14y ago

Just out of curiosity, if you had a web app like Gmail, and your user accidentally went to close their browser window with an unsaved email half done, how would you plan on warning them without blocking events?

svachalek 14y ago
Save it in drafts and notify them when they come back.
- JoeCortopassi 14y ago
  So Facebook and Twitter should also save drafts of posts you were going to make? What if latency is non-trivial, or connection is lost? Do I also want to send ajax posts for drafts every second to ensure that as little as possible is lost? A lot of this is mitigated by a very simple confirm("Are you sure you want to leave?");
  - kevincennis 14y ago
    Twitter actually does save drafts in localStorage.
  - ianstormtaylor 14y ago
    Yeah but for all the times when I really do want to leave, now I have to annoyingly click "Yes" in a dialog I didn't expect in the first place. I like the localStorage solution for drafts much better.
teraflop 14y ago
You use the onbeforeunload event, which doesn't block the event thread. (EDIT: actually it does, just not while JS code is executing, unlike alert().) In fact, the HTML5 spec permits browsers to disregard the normal blocking behavior of alert()/confirm()/prompt() (making them no-ops) while this event is being handled: https://developer.mozilla.org/en-US/docs/DOM/window.onbeforeunloadwhile https://developer.mozilla.org/en-US/docs/DOM/window.onbefore... the dialog box is open
- teraflop 14y ago
  I managed to break that link somehow and can no longer edit it, here's the correct one: https://developer.mozilla.org/en-US/docs/DOM/window.onbeforeunload https://developer.mozilla.org/en-US/docs/DOM/window.onbefore...