This API method allows user script authors to persist simple values locally.
Strings, booleans, and integers are currently the only allowed data types. This places limitations on the size of an individual value, and the number of values.
Values are saved in the Firefox preferences back end and can be manually changed by typing
about:config in the address bar and searching for the preference name "greasemonkey.scriptval.script-namespace/script-name".
GM_setValue( name, value )
- Value: String
name = "PropertyName";
- Property name to retrieve or create.
- Value: String, Integer or Boolean
value = 5;
 The previous incarnation of this article had an example of
alert(GM_setValue("foo", "bar"));. Currently miscapis.js and prefmanager.js does not have any