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Asked: 2026-05-10T21:41:43+00:00

This question deals with concurrency issues, for suggestions on how to display a busy

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This question deals with concurrency issues, for suggestions on how to display a busy icon see this question: Javascript – loading/busy indicator or transparent div over page on event click

When a user initiates an AJAX request on a page it’s useful to show some kind of ‘working’ or busy icon or progress indicator. If there is only one long-running process this can be handled in a relatively straightforward way:

function do_action() {    show_busy_icon();            long_running_asynchronous_process(function() {       // Callback function run when process finishes       hide_busy_icon();    }); }

However, if multiple asynchronous processes are running on the page, using on/off methods wouldn’t work. The first process to finish switches off the icon even though there are additional processes running.

So, how do you handle displaying an indicator, on a web page, that is on when there are one or more processes running, and off when there are no processes running?

I imagine it would be possible to maintain a count of the number of processes running. hide_busy_icon() only hides the icon if the process count is 0. That seems kinda prone to failure. Perhaps there’s a better/simpler way that I’m not seeing.

Thanks for your ideas and suggestions!

Edit: After working with the solution in the marked answer for a while, I’m happy to say it works very well. The only issue I’ve run into are cases where my own scripts call functions of scripts I don’t control. Unless those functions allow callbacks to be supplied there’s no way to update the process-count when they begin and end.

An example of where this can occurs is adding a set of markers to a Google map. Once my script calls the Google maps function the busy icon disappears, while the markers are still being loaded.

I’m not sure of a good way to handle this.

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1 Answer

  1. If you want the same busy indicator for all actions, then use a counter.

    Instead of ‘show_busy_icon()’, do a ‘increment_busy_count()’, which calls ‘show_busy_icon()’ if busy count goes from 0 to 1. Instead of ‘hide_busy_icon()’, do a ‘decrement_busy_count()’, which calls ‘hide_busy_icon()’ if busy count goes from 1 to 0.

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