MDN’s new design is in Beta! A sneak peek: https://blog.mozilla.org/opendesign/mdns-new-design-beta/

Add-ons using the techniques described in this document are considered a legacy technology in Firefox. Don't use these techniques to develop new add-ons. Use WebExtensions instead. If you maintain an add-on which uses the techniques described here, consider migrating it to use WebExtensions.

From Firefox 53 onwards, no new legacy add-ons will be accepted on addons.mozilla.org (AMO).

From Firefox 57 onwards, WebExtensions will be the only supported extension type, and Firefox will not load other types.

Even before Firefox 57, changes coming up in the Firefox platform will break many legacy extensions. These changes include multiprocess Firefox (e10s), sandboxing, and multiple content processes. Legacy extensions that are affected by these changes should migrate to WebExtensions if they can. See the "Compatibility Milestones" document for more.

A wiki page containing resources, migration paths, office hours, and more, is available to help developers transition to the new technologies.

Experimental

Building blocks for composing lists.

Globals

Constructors

List(element1, element2, ...)

Constructor can takes any number of elements and creates an instance of List populated with the specified elements.

Parameters

element1 : Object|String|Number

element2 : Object|String|Number

... : Object|String|Number

Functions

addListItem(list, item)

Function adds a item to a List.

removeListItem(list, item)

Function removes an item from a List

List

An ordered collection (also known as a sequence) disallowing duplicate elements. List is composed out of Iterable, therefore it provides custom enumeration behavior that is similar to array (enumerates only on the elements of the list).

List is a base trait and is meant to be part of a composition, since all of its API is private except for the length property.

Examples:

var { List } = require("sdk/util/list");
var MyList = List.compose({
  add: function add(item1, item2, /*item3...*/) {
    Array.slice(arguments).forEach(this._add.bind(this));
  },
  remove: function remove(item1, item2, /*item3...*/) {
    Array.slice(arguments).forEach(this._remove.bind(this));
  }
});
MyList('foo', 'bar', 'baz').length == 3;        // true
new MyList('new', 'keyword').length == 2;       // true
MyList.apply(null, [1, 2, 3]).length == 3;      // true
let list = MyList();
list.length == 0;                               // true
list.add(1, 2, 3) == 3;                         // true

Properties

length

Number of elements in this list.

Document Tags and Contributors

 Contributors to this page: wbamberg, evold, jsantell
 Last updated by: wbamberg,