When attempting to utilize nsIPrefBranch in a Firefox extension to save data, an unexpected error of NS_ERROR_UNEXPECTED occurs

I am facing a challenge with saving persistent data in a Firefox extension.

Currently, I am attempting to utilize nsIPrefBranch in the following manner:

var db = Components.classes["@mozilla.org/preferences-service;1"].getService(Components.interfaces.nsIPrefBranch);
if(db.getCharPref('epoch')){ ///do something.. }

However, this approach does not seem to be effective as I keep encountering the following error:

"Component returned failure code: 0x8000ffff (NS_ERROR_UNEXPECTED) [nsIPrefBranch.getCharPref]"

Could someone please shed some light on what mistake I may be making?

javascriptfirefox-addon

Answer №1

The term "epoch" is not a recognized preference - this message indicates that you need to set this preference before using getCharPref(). To handle potential errors, it's common for extensions to encapsulate calls to nsIPrefBranch in try .. catch blocks.

Additionally, preferences function as a shared space (viewable under about:config). It's important to specify that a preference belongs to your extension to avoid conflicts with other extensions or browser preferences. For example, consider using a naming convention like "extensions.myExtension.epoch" instead of just "epoch".

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