Navigator.plugins, mimeTypes, pdfViewerEnabled updates (#13605)

* Navigator.plugins, mimeTypes, pdfViewerEnabled updates

* Apply suggestions from code review

Co-authored-by: Joe Medley <jmedley@google.com>

* Update files/en-us/web/api/navigator/pdfViewerEnabled/index.md

Co-authored-by: Joe Medley <jmedley@google.com>

* lower case the file name

* revert slug

Co-authored-by: Joe Medley <jmedley@google.com>

files/en-us/web/api/navigator/index.md

@@ -57,6 +57,8 @@ _Doesn't inherit any properties._
   - : Returns {{domxref("MediaSession")}} object which can be used to provide metadata that can be used by the browser to present information about the currently-playing media to the user, such as in a global media controls UI.
 - {{domxref("Navigator.onLine")}} {{readonlyInline}}
   - : Returns a boolean value indicating whether the browser is working online.
+- {{domxref("Navigator.pdfViewerEnabled")}} {{readonlyinline}}
+  - : Returns `true` if the browser can display PDF files inline when navigating to them, and `false` otherwise.
 - {{domxref("Navigator.permissions")}} {{readonlyinline}} {{experimental_inline}}
   - : Returns a {{domxref("Permissions")}} object that can be used to query and update permission status of APIs covered by the [Permissions API](/en-US/docs/Web/API/Permissions_API).
 - {{domxref("Navigator.presentation")}} {{readonlyInline}} {{experimental_inline}}

files/en-us/web/api/navigator/mimetypes/index.md

@@ -6,43 +6,49 @@ tags:
   - Property
   - Navigator
   - Reference
+  - Deprecated
 browser-compat: api.Navigator.mimeTypes
 ---
 {{ ApiRef("HTML DOM") }}{{deprecated_header}}
 
-Returns a {{domxref("MimeTypeArray")}} object, which contains a list of
-{{domxref("MimeType")}} objects representing the MIME types recognized by the browser.
+Returns a {{domxref("MimeTypeArray")}} object, which contains a list of {{domxref("MimeType")}} objects representing the MIME types recognized and supported by the browser.
+The array can be queried for information about the enabled plugin that is used to handle a file of the specified type.
+Named properties of the returned object are not enumerable (except in very old browser versions).
 
-> **Note:** Named properties of {{domxref("MimeTypeArray")}} objects are
-> no longer enumerable in the latest browser versions.
+Recent versions of the specification hard-code the returned set of MIME types.
+If PDF files can be displayed inline then `application/pdf` and `text/pdf` are listed.
+Otherwise an empty list is returned.
 
-## Syntax
+> **Note:** Use {{domxref("Navigator.pdfViewerEnabled")}} to determine if inline viewing of PDF files is supported. Do not infer it from this property.
 
-```js
-var mimeTypes[] = navigator.mimeTypes;
-```
+Legacy browser versions do not hard-code the list returned by the property, and might return other MIME types.
+
+
+## Value
 
-`mimeTypes` is a `MimeTypeArray` object which has a
-`length` property as well as `item(index)` and
-`namedItem(name)` methods.
+A `MimeTypeArray` object which has a `length` property as well as `item(index)` and `namedItem(name)` methods.
+
+If PDF inline viewing is supported this has entries for MIME types `application/pdf` and `text/pdf`.
+Otherwise an empty `MimeTypeArray` is returned.
+The description and file suffixes supported by enabled plugins are hard coded to `'pdf'` and `'Portable Document Format'`, respectively.
 
 ## Example
 
+The code below tests whether PDF files can be viewed inline, and then prints the description of the plugin and the file suffixes it supports.
+
 ```js
-function isJavaPresent() {
-  return 'application/x-java-applet' in navigator.mimeTypes;
-}
+if ('application/pdf' in navigator.mimeTypes) { 
+  // browser supports inline viewing of PDF files.
 
-function getJavaPluginDescription() {
-  var mimetype = navigator.mimeTypes['application/x-java-applet'];
-  if (mimetype === undefined) {
-    // no Java plugin present
-    return undefined;
-  }
-  return mimetype.enabledPlugin.description;
+  const { description, suffixes } = navigator.mimeTypes['application/pdf'];
+  console.log(`Description: ${ description }, Suffix: ${ suffixes }`);
+  // expected output: Description: Portable Document Format, Suffix: pdf
 }
 ```
 
+Note that while the above code tests for `application/pdf` you could equally well check `text/pdf`. (Either both or neither MIME type will be true.)
+In addition, on current browsers you don't actually need to get the plugin description and suffixes, because this information is also hard-coded.
+
 ## Specifications
 
 {{Specifications}}

files/en-us/web/api/navigator/pdfviewerenabled/index.md

@@ -0,0 +1,40 @@
+---
+title: Navigator.pdfViewerEnabled
+slug: Web/API/Navigator/pdfViewerEnabled
+tags:
+  - pdfViewerEnabled
+  - API
+  - DOM
+  - Property
+  - Reference
+browser-compat: api.Navigator.pdfViewerEnabled
+---
+{{APIRef("HTML DOM")}}
+
+The **`pdfViewerEnabled`** property of the {{domxref("Navigator")}} interface indicates whether the browser supports inline display of PDF files when navigating to them.
+
+If inline viewing is not supported the PDF is downloaded and may then be handled by some external application.
+
+> **Note:** This method replaces a number of legacy methods of inferring support for inline viewing of PDF files.
+
+## Value
+
+`true` if the browser can display PDF files inline when navigating to the file (using either an internal viewer or a PDF viewer extension); otherwise `false`.
+
+## Examples
+
+To check PDF inline viewing support:
+
+```js
+if (!navigator.pdfViewerEnabled) {
+  // The browser does not support inline viewing of PDF files.
+}
+```
+
+## Specifications
+
+{{Specifications}}
+
+## Browser compatibility
+
+{{Compat}}

files/en-us/web/api/navigator/plugins/index.md

@@ -8,89 +8,55 @@ tags:
   - Plugins
   - Property
   - Reference
+  - Deprecated
 browser-compat: api.Navigator.plugins
 ---
 {{APIRef("HTML DOM")}}{{deprecated_header}}
 
-Returns a {{DOMxRef("PluginArray")}} object, listing the {{DOMxRef("Plugin")}} objects
-describing the plugins installed in
-the application.
+Returns a {{DOMxRef("PluginArray")}} object, listing the {{DOMxRef("Plugin")}} objects describing the plugins installed in the application.
+Named properties of returned object are not enumerable (except in very old browser versions).
 
-> **Note:** In Firefox 29 and later, enumeration of the `navigator.plugins` array may
-> be restricted as a privacy measure. Applications that must check for the presence of a
-> browser plugin should query `navigator.plugins` or
-> {{DOMxRef("Navigator.mimeTypes", "navigator.mimeTypes")}} by exact name instead of enumerating the
-> `navigator.plugins` array and comparing every plugin's name. This privacy
-> change does not disable any plugins; it just hides some plugin names from enumeration.
+Recent versions of the specification hard-code the returned list.
+If inline viewing of PDF files is supported the property lists five standard plugins
+If inline PDF viewing is not supported then an empty list is returned.
 
-## Syntax
+> **Note:** Use {{domxref("Navigator.pdfViewerEnabled")}} to determine if inline viewing of PDF files is supported. Do not infer it from this property.
+>
+> The "five standard plugins" are those that developers have most commonly used to feature detect inline PDF viewing.
+> Returning these ensures that legacy code can more reliably determine whether inline viewing is supported. 
+> However this approach is not recommended for new code because this property may eventually be removed.
 
-```js
-var plugins = navigator.plugins;
-```
+Legacy browser versions also list plugins for Adobe Flash and PDF viewer extensions.
 
-`plugins` is {{DOMxRef("PluginArray")}} object used to access
-{{DOMxRef("Plugin")}} objects either by name or as a list of items.
+## Value
 
-The returned value is not a JavaScript array, but has the `length` property
-and supports accessing individual items using bracket notation
-(`plugins[2]`), as well as via `item(index)` and
-`namedItem("name")` methods.
-
-## Examples
+`plugins` is a {{DOMxRef("PluginArray")}} object used to access {{DOMxRef("Plugin")}} objects either by name or as a list of items.
 
-The following example function returns the version of the Shockwave Flash plugin.
-
-```js
-function getFlashVersion() {
-  var flash = navigator.plugins.namedItem('Shockwave Flash');
-  if (typeof flash != 'object') {
-    // flash is not present
-    return undefined;
-  }
-  if(flash.version){
-    return flash.version;
-  } else {
-    //No version property (e.g. in Chrome)
-    return flash.description.replace(/Shockwave Flash /,"");
-  }
-}
-```
+The returned value is not a JavaScript array, but has the `length` property and supports accessing individual items using bracket notation (`plugins[2]`), as well as via `item(index)` and `namedItem("name")` methods.
 
-The following example displays information about the installed plugin(s).
+If PDF inline viewing is supported this will contain entries for the following plugins:
+- "PDF Viewer"
+- "Chrome PDF Viewer"
+- "Chromium PDF Viewer"
+- "Microsoft Edge PDF Viewer"
+- "WebKit built-in PDF"
+If inline viewing of PDFs is not supported then an empty object is returned.
 
-```js
-var pluginsLength = navigator.plugins.length;
 
-document.body.innerHTML = pluginsLength + " Plugin(s)<br>"
-  + '<table id="pluginTable"><thead>'
-  +'<tr><th>Name</th><th>Filename</th><th>description</th><th>version</th></tr>'
-  +'</thead><tbody></tbody></table>';
+## Examples
 
-var table = document.getElementById('pluginTable');
+This code shows how to check if PDF files can be displayed inline:
 
-for(var i = 0; i < pluginsLength; i++) {
-  let newRow = table.insertRow();
-  newRow.insertCell().textContent = navigator.plugins[i].name;
-  newRow.insertCell().textContent = navigator.plugins[i].filename;
-  newRow.insertCell().textContent = navigator.plugins[i].description;
-  newRow.insertCell().textContent = navigator.plugins[i].version?navigator.plugins[i].version:"";
+```js
+if ('PDF Viewer' in navigator.plugins) { 
+  // browser supports inline viewing of PDF files.
 }
 ```
 
-## Notes
-
-The {{DOMxRef("Plugin")}} object exposes a small interface for getting information
-about the various plugins installed in your browser. A list of plugins is also available
-by entering `about:plugins` in the browser's Location bar.
-
 ## Specifications
 
 {{Specifications}}
 
 ## Browser compatibility
 
 {{Compat}}
-
-In addition to listing each plugin as a pseudo-array by zero-indexed numeric
-properties, Firefox provides properties that are the plugin name directly on the [PluginArray](/en-US/docs/Web/API/PluginArray) object.