Firefox 50 para desarrolladores

Firefox 50 was released on November 15, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.

Cambios para desarrolladores Web

HTML

El estilo por defecto <bdo> ahora asigna unicode-bidi con el valor isolate-override (Error 1249497 en Firefox).
Asignar el atributo src del elemento <track> ahora funciona correctamente (Error 1281418 en Firefox).
El atributo referrerpolicy en los elementos <area>, <a>, <img>, <iframe> y <link> ahora está disponible por defecto (Error 1223838 en Firefox, Error 1264165 en Firefox).

CSS

Esquinas con estilos punteados y rayados (dashed, dotted) Border-radiused ahora son mostradas con el estilo especificado en lugar de estilo sólido (Error 382721 en Firefox).
El selector pseudo-clase no estándar :-moz-full-screen-ancestor fue removido (Error 1199529 en Firefox).
box-sizing: padding-box fue removido, dado que ya no forma parte de la especificación y Firefox era el unico entre los principales navegadores que lo implementaba (Error 1166728 en Firefox).
Se removió el prefijo de los tres valores isolate, isolate-override, y plaintext de la propiedad unicode-bidi (Error 1141895 en Firefox).
En modo de compatibilidad, la etiqueta de un elemento de lista ahora hereda el tamaño de la lista, como en el modo estandar (Error 648331 en Firefox).
Las pseudo-clases :in-range y :out-of-range cambiaron su comportamiento para no coincidir elementos input deshabilitados o de solo lectura (Error 1264157 en Firefox).
Se removió el prefijo de la pseudo-clase :any-link(Error 843579 en Firefox).
El valor space para border-image-repeat fue implementado (Error 720531 en Firefox).

JavaScript

La propiedad del ES2015 Symbol.hasInstance ha sido implementada (Error 1054906 en Firefox).
El método de ES2017 Object.getOwnPropertyDescriptors() ha sido implementado (Error 1245024 en Firefox).
El comportamiento de \W in RegExp con los flags unicode e ignoreCase cambió para estar de acuerdo con el borrador mas reciente de la especificación. Ahora no coincide con K, S, k, s, and KELVIN SIGN (U+212A), y LATIN SMALL LETTER LONG S (U+017F) (Error 1281739 en Firefox).

Herramientas de desarrollador

La consola Web ahora entiende los source maps.
El inspector de almacenamiento ahora permite borrar elementos individuales desde los objetos de almacenamiento de IndexedDB.
La herramienta de memoria está habilitada por defecto.
La panel de "Modelo de caja" fue movido al panel lateral Computado.
La consola Web ahora muestra las trazas de pila para las peticiones de red XHR o Fetch().
Todos los bugs corregidos entre Firefox 49 y Firefox 50.

HTTP

El protocolo experimental (y obsoleto) SPDY 3.1 ahora está deshabilitado por defecto Error 1287132 en Firefox.
Se añadió soporte para X-Content-Type-Options (Error 471020 en Firefox).
Los prefijos de cookies __Host- and __Secure- han sido implementados. Ver Set-Cookie y Error 1283368 en Firefox.
El encabezado Referrer-Policy ha sido implementado Error 1264164 en Firefox.

Seguridad

El atributo ping del elemento <a> ahora se apega al connect-src CSP 1.1 policy directive (Error 1100181 en Firefox).
Agregado soporte para la directiva sandbox CSP (Error 671389 en Firefox).
Ahora es posible indicar una política content security policy for workers (Error 959388 en Firefox).
El método Navigator.sendBeacon() ya no lanza una excepción si los datos de la baliza (Beacon Data) no pudieron ser enviados devido a una política de restricción consentimiento method Content Security Policy; en su lugar, retorna false como es esperado (Error 1234813 en Firefox).

Redes

Cuando un error es encontrado durante una XMLHttpRequest asíncrona, el método XMLHttpRequest.getAllResponseHeaders() ahora retorna un string vacio (Error 1286744 en Firefox).
En lugar de retornar un NetworkError, ahora el asynchronous XMLHttpRequest asíncrono que falla por CORS u otras restricciones de red, ahora lanza un error que puede ser capturado como cualquier otro error (Error 709991 en Firefox).
XMLHttpRequest.getResponseHeader() y XMLHttpRequest.getAllResponseHeaders() ahora también retornan encabezados vacíos por defecto. Esto puede ser controlado mediante la preferencia network.http.keep_empty_response_headers_as_empty_string (Error 918721 en Firefox).
La opción only-if-cached fue agregada a Request.cache (Error 1272436 en Firefox).

DOM

Ahora la opción once para EventTarget.addEventListener() es soportada (Error 1287706 en Firefox).
La interfaz NodeList are now iterable and the methods forEach(), values(), NodeList.entries() and NodeList.keys() are now available (Error 1290636 en Firefox).
The interface DOMTokenList are now iterable and the methods forEach(), values(), DOMTokenList.entries() and DOMTokenList.keys() are now available (Error 1290636 en Firefox).
The methods Document.createElement() and Document.createElementNS() now have an optional options parameter for creating custom elements (Error 1276579 en Firefox).

SVG

The allowReorder attribute has been dropped and the behavior it was setting is now the default for SVG <switch> elements (Error 1279690 en Firefox).
The defer keyword for the preserveAspectRatio attribute on SVG <image> elements has been removed to follow the latest SVG2 specification (Error 1280425 en Firefox).

Drag and Drop API

The DataTransfer.items property has been implemented, allowing access to multiple items being dragged and dropped using the HTML Drag and Drop API. To allow this, the DataTransferItem and DataTransferItemList interfaces are now supported as well (Error 906420 en Firefox). This is enabled by default.
The old, obsolete Firefox specific drag and drop API events dragdrop and draggesture are no longer supported. Be sure to update any code still using them to use the HTML drag and drop API (Error 1162050 en Firefox.

Pointer Lock API

The Pointer Lock API is now unprefixed (Error 991899 en Firefox).
Before Firefox 50, requestPointerLock() asked for permission using a doorhanger, and pointer lock would not be enabled until the user granted permission. From Firefox 50, pointer lock is like the fullscreen API: it's granted immediately, but a notification is displayed explaining to the user how to exit (Error 1273351 en Firefox).

IndexedDB

Ahora se envía un evento close al objeto IDBDatabase cuando la base de datos respectiva es cerrada de forma inesperada (Error 1151017 en Firefox).

Service Workers

The WindowClient.navigate() method has been implemented. This method lets you open a specified URL into a client window which is being controlled by the service worker (Error 1218148 en Firefox).

WebGL

The EXT_shader_texture_lod WebGL extension has been implemented (Error 1111689 en Firefox).
The texImage methods have been updated for WebGL 2 to implement PBOs (PIXEL_UNPACK_BUFFER) (Error 1280499 en Firefox).

WebRTC

Adding a track to a MediaStream now generates the addtrack event as described in the specification. The event is of type MediaStreamTrackEvent and is fired on the stream to which the track was added. You can use either MediaStream.addEventListener('addtrack', ...) or the MediaStream.onaddtrack property to handle "addtrack" events.
The MediaStreamTrack interface now supports the ended event and the MediaStreamTrack.onended event handler.
Firefox now supports the MediaStreamTrack.readyState property, which indicates whether the track is live or permanently ended.
The MediaStreamTrack methods getConstraints() and getSettings() have been implemented; these let you get the most recently applied set of customized property constraints and the actual values of all of the track's constrainable properties, respectively. The accompanying data types have been documented as well.
The RTCDataChannel.stream property has been removed. This was replaced with RTCDataChannel.id in Firefox 24, but was supported for backward compatibility. Please be sure to update your code to use the id property if you haven't done so yet.

Web Audio API

The PannerNode interface now supports the 3D Cartesian space properties for the position (PannerNode.positionX, PannerNode.positionY, and PannerNode.positionZ) and directionality (PannerNode.orientationX, PannerNode.orientationY, PannerNode.orientationZ) of an audio source.
The interface IIRFilterNode, which implements a general infinite impulse response (IIR) filter, has been implemented.
Throttling in background tabs of timers created by Window.setInterval() and Window.setTimeout() no longer occurs if a Web Audio API AudioContext is actively playing sound. This should help prevent issues with timing-sensitive audio playback (such as music players generating individual notes using timers) in the background (Error 1181073 en Firefox).

Audio/Video

The AlignSetting enum (representing possible values for VTTCue.align) incorrectly previously included the value "middle" instead of "center". This has been corrected (Error 1276130 en Firefox).
The non-standard and experimental method HTMLMediaElement.seekToNextFrame() now seeks to the next frame in the media asynchronously, rather than synchronously, and returns a Promise which resolves once the seek is complete.
The implementation of HTMLTrackElement has been corrected to allow <track> elements to load resources even if not in a document (Error 871747 en Firefox).

API de batería

The navigator.battery property, which has been deprecated since Firefox 43, is now obsolete and has been removed. Use the navigator.getBattery() method instead to get a battery Promise, which will resolve when the BatteryManager is available for use; the BatteryManager is passed into the fulfillment handler for the promise (Error 12593355 en Firefox).

Archivos y directorios

A subset of the File and Directory Entries API has been implemented, to improve compatibility with sites that were previously only compatible with Google Chrome (Error 1265767 en Firefox).
- The asynchronous API interfaces have been implemented, with the caveat that only reading of files is supported; for example, the FileSystemFileEntry.createWriter() method is a no-op.
- These interfaces have been implemented:
  - FileSystem
  - FileSystemEntry (properties only; the methods have not been implemented)
  - FileSystemFileEntry (except for createWriter())
  - FileSystemDirectoryEntry (except for removeRecursively())
  - FileSystemDirectoryReader
- HTMLInputElement.webkitdirectory as well as the webkitdirectory attribute of the <input> element have been implemented; this lets you configure a file input to accept directories instead of files (Error 1258489 en Firefox).
- HTMLInputElement.webkitEntries has been implemented; this returns an array of FileSystemEntry-based objects representing the selected items.
- File.webkitRelativePath has been implemented; this contains the path of the file relative to the root of the containing FileSystemDirectoryEntry that was among the items in the list returned by HTMLInputElement.webkitGetEntries().
- See File and Directory Entries API support in Firefox for details about what we do and do not support in this API.
- These APIs are now enabled by default; some were previously available but only behind a preference (Error 1288683 en Firefox).
We've implemented DataTransferItem.webkitGetAsEntry() as part of the File and Directory Entries API; this lets you obtain a FileSystemEntry representing a dropped file (Error 1289255 en Firefox). This is enabled by default.
The HTMLInputElement.directory property, part of the Directory Upload API proposal, has been renamed to allowdirs (Error 1288681 en Firefox). This property is hidden behind a preference.