« XUL Reference home
getFormattedString( key, strArray )
Return type: string
Looks up the format string for the given key name in the string bundle and returns a formatted copy where each occurrence of %S (uppercase) is replaced by each successive element in the supplied array. Alternatively, numbered indices of the format %n$S (e.g. %1$S, %2$S, etc.) can be used to specify the position of the corresponding parameter explicitly.

If you need to handle substitutions involving plurals, take a look at Localization and Plurals.