Dom.max script run time

From MozillaZine Knowledge Base

The title given to this article is incorrect due to technical limitations. The correct title is dom.max_script_run_time.

This article describes the preference dom.max_script_run_time. To add, delete, or modify this preference, you will need to edit your configuration — do not edit this article.

1 Background
2 Possible values and their effects
3 Previous effects
4 Caveats
5 Recommended settings
6 First checked in
7 Has an effect in
8 Related bugs
9 Related preferences

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Background

“[JavaScript] that executes for whole seconds is probably doing something wrong...” says Brendan Eich, creator of JavaScript. When a script is executing, Mozilla's UI will be unresponsive until the script’s thread ends. Correspondingly, Mozilla will alert you when a script is taking a long time to run and let you stop the script. This preference lets you define what “a long time” is.

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Possible values and their effects

The value is a positive integer, determining the number of seconds of execution. 0 and negative values are considered "forever." (Default value is 5; 10 in nightly builds after 2006-07-27)

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Previous effects

In builds prior to 2005-10-11, values less than 0 were assumed to be the default (then, 5). In builds prior to 2006-07-27 (e.g., Firefox 1.5), this preference affected scripts running in content and chrome; the limit on scripts running in chrome is now determined by dom.max_chrome_script_run_time.

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Caveats

This preference was not dynamic (i.e., only read at startup) until recently (2005-10-11). The new dynamic behavior is available in Mozilla Firefox 1.5 branch builds, Mozilla Thunderbird branch builds, and SeaMonkey.
This preference was subject to some bugs (see below) that made the true time limit somewhat unpredictable for certain scripts.

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Recommended settings

If you’re encountering the “A script on this page is causing Mozilla to run slowly” dialog often and you’d like to disable it, setting this preference to 0 will allow the script to run for as long as it needs. A large number may be more appropriate, though, to avoid locking the entire UI forever as the script executes.

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