API Reference: Prefs.jsm library

API Reference

Prefs.jsm library

What is the User Preferences?

• nsIPrefBranch - MDC

• Preferences - MDC

Remarks #1

Every preferences have a type. There are three simple types and some complex types.

• boolean
• integer
• string
• and some complex types.
  

Remarks #2

Don't overlap your preference's name to others. Keep to use your original branch (ex. "extensions." or something like that) is a good manner.

Example #1: How to handle the "javascript.options.strict" preference.

• Construct a instance of Prefs Class.

//Specify a branch. Note: you must terminate it with a period.
var prefs = new Prefs("javascript.options.");

• Set the value of preference to true.

prefs.set("strict", true);

• Get the value of preference.

var v = prefs.get("strict");

That's all. The library can infer a proper type for the preference automatically (and you can specify it manually if you want).

Reference Manual

function: Prefs aBranchName
Construct a new instance.
aBranchName A branch's name. String. You must terminate it with a period.

function: get aPrefName &optional aDefaultValue aType
Get the value of preference.
aPrefName A preference's name. String.
aDefaultValue A return value when the function failed to get.
aType A type of preference. String. Please see the table.1 below.

function: set aPrefName aValue &optional aType aRelFileRelativeToKey
Set the value of preference.
aPrefName A preference's name. String.
aValue A value to set.
aType A type of preference. String. Please see the table.2 below.
aRelFileRelativeToKey A keyword for the relative file path's root directory(ex. "ProfD", etc). String.

function: clear aPrefName
Clear the preference.
aPrefName A preference's name. String.

function: getChildList &optional aStartingAt
Get the array of preferences' name of below the branch.
aStartingAt A branch's name. String.

Table.1: aType for get

type	aType	calls internally
boolean	"boolean"	getBoolPref(aPrefName)
integer	"integer"	getIntPref(aPrefName)
string	"string"	getComplexValue(aPrefName, Ci.nsISupportsString).data
localized string	"localized"	getComplexValue(aPrefName, Ci.nsIPrefLocalizedString).data
absolute file path	"file"	getComplexValue(aPrefName, Ci.nsILocalFile)
relative file path	"relFile"	getComplexValue(aPrefName, Ci.nsIRelativeFilePref)

Table.2: aType for set

type	aType	calls internally
boolean	"boolean"	setBoolPref(aPrefName, !!aValue)
integer	"integer"	setIntPref(aPrefName, +aValue)
string	"string"	setComplexValue(aPrefName, Ci.nsISupportsString, nsISupportsString's instance)
localized string	"localized"	setComplexValue(aPrefName, Ci.nsIPrefLocalizedString, nsIPrefLocalizedString's instance
absolute file path	"file"	setComplexValue(aPrefName, Ci.nsILocalFile, aValue)
relative file path	"relFile"	setComplexValue(aPrefName, Ci.nsIRelativeFilePref, nsIRelativeFilePref's instance)

Please refer the File I/O - MDC about the relative file path.