Why "Prevent this page from creating additional dialogs" appears in the alert box?

Question

In my Rails 3 application I do:

render :js => "alert(\"Error!\\nEmpty message sent.\");" if ...

Sometimes, below this error message (in the same alert box) I see: "Prevent this page from creating additional dialogs" and a checkbox.

What does this mean ?

Is that possible not to display this additional text and checkbox ?

I use Firefox 4.

Solution 1

It's a browser feature to stop websites that show annoying alert boxes over and over again.

As a web developer, you can't disable it.

Solution 2

What does this mean ?

This is a security measure on the browser's end to prevent a page from freezing the browser (or the current page) by showing modal (alert / confirm) messages in an infinite loop. See e.g. here for Firefox.

You can not turn this off. The only way around it is to use custom dialogs like JQuery UI's dialogs.

Solution 3

You can create a custom alert box using java script, below code will override default alert function

window.alert = function(message) { $(document.createElement('div'))
    .attr({
      title: 'Alert',
      'class': 'alert'
    })
    .html(message)
    .dialog({
      buttons: {
        OK: function() {
          $(this).dialog('close');
        }
      },
      close: function() {
        $(this).remove();
      },
      modal: true,
      resizable: false,
      width: 'auto'
    });
};

Comments

[Ankur]

The browser think that you js code has some bug and it is showing the message very frequently in some sort of loop and hence browser provide the option to user to disallow this alert box

[Shadow The Kid Wizard]

Chrome show this from the second alert onwards regardless of the content or length of these alerts..

[Dan Bechard]

@ShadowWizard As of today, it seems to be based on elapsed time since previous alert was closed. The timer is around a second or so.

[Shadow The Kid Wizard]

@Dan yeah, probably they changed it over the years. :)

[Marcel Korpel]

Just to add: from Firefox 4 onwards those alerts are not modal anymore, at least not to the window manager. You can easily navigate away to other tabs/windows nowadays.

[GalacticCowboy]

"alert and confirm is the only way to stop the execution of a script at a certain point" - When you're thinking synchronously, that's true. However, these can use the jQueryUI controls to fire another method that then handles the result.

[mozey]

It is true when you're thinking asynchronously as well. Using callbacks does not stop code executing in between. But as you say, passing in a callback function is a great way to control flow when using the jQuery dialogs.

[drooh]

Can you show how to use this? Maybe add a little description of how to use and whats happening?