This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
settingValue property of the
MozSettingsEvent object returns the setting's new value.
var value = instanceOfMozSettingsEvent.settingValue;
Typically a string or number, this is the value of the affected setting.
Not part of any specification yet; however, this API will be discussed at W3C as part of the System Applications Working Group.