正在翻譯中。

附加元件是一群檔案的集合,作為的發布及安裝的目的而包裝成一個檔案。在這個章節,我們將快速地討論可能會放附加元件中的檔案。

manifest.json

這是每個附加元件中,唯一一個必要放置的檔案。它包含了附加元件的名稱、版本、及需要的權限等資訊,同時也提供了附加元件中其他檔案的路徑指標。

這份manifest也可以包含幾項其他種類檔案的指標路徑:

參考 manifest.json 參考頁取得全部的明細。

除了那些參考自manifest之外,附加元件可以包含額外支援的檔案作為 Extension pages

Background scripts 後台腳本

擴展套件通常需要保持長期狀態或長時間執行操作,而生命週期不依賴於任何特定網頁或瀏覽器視窗。這是後台腳本的用途。

後台腳本會在擴充套件讀取時立即執行且會持續執行直到擴充套件被禁用或是解除安裝。你可以在腳本裡使用任何WebExtension APIs, 只要你已經申請了必要的權限。

Specifying background scripts

你可以在"manifest.json"裡使用background關鍵字用來包含後台腳本。

// manifest.json

"background": {
  "scripts": ["background-script.js"]
}

You can specify multiple background scripts: if you do, they run in the same context, just like multiple scripts that are loaded into a single web page.

Background script environment 後台腳本環境

DOM APIs

Background scripts run in the context of special pages called background pages. This gives them a window global, along with all the standard DOM APIs provided by that object.

You do not have to supply your background page. If you include a background script, an empty background page will be created for you.

However, you can choose to supply your background page as a separate HTML file:

// manifest.json

"background": {
  "page": "background-page.html"
}

WebExtension APIs

Background scripts can use any of the WebExtension APIs in the script, as long as their extension has the necessary permissions.

Cross-origin access 跨域請求

Background scripts can make XHR requests to any hosts for which they have host permissions.

Web content

Background scripts do not get direct access to web pages. However, they can load content scripts into web pages and can communicate with these content scripts using a message-passing API.

Content security policy

Background scripts are restricted from certain potentially dangerous operations, like the use of eval(), through a Content Security Policy. See Content Security Policy for more details on this.

Your extension can include various user interface components whose content is defined using an HTML document:

  • a sidebar is a pane that is displayed at the left-hand side of the browser window, next to the web page
  • a popup is a dialog that you can display when the user clicks on a toolbar button or address bar button
  • an options page is a page that's shown when the user accesses your add-on's preferences in the browser's native add-ons manager.

For each of these components, you create an HTML file and point to it using a specific property in manifest.json. The HTML file can include CSS and JavaScript files, just like a normal web page.

All of these are a type of Extension pages, and unlike a normal web page, your JavaScript can use all the same privileged WebExtension APIs as your background script. They can even directly access variables in the background page using runtime.getBackgroundPage().

Extension pages擴充頁面

You can also include HTML documents in your extension which are not attached to some predefined user interface component. Unlike the documents you might provide for sidebars, popups, or options pages, these don't have an entry in manifest.json. However, they do also get access to all the same privileged WebExtension APIs as your background script.

You'd typically load a page like this using windows.create() or tabs.create().

See Extension pages to learn more.

Content scripts

Use content scripts to access and manipulate web pages. Content scripts are loaded into web pages and run in the context of that particular page.

Content scripts are extension-provided scripts which run in the context of a web page; this differs from scripts which are loaded by the page itself, including those which are provided in <script> elements within the page.

Content scripts can see and manipulate the page's DOM, just like normal scripts loaded by the page.

Unlike normal page scripts, they can:

  • Make cross-domain XHR requests.
  • Use a small subset of the WebExtension APIs.
  • Exchange messages with their background scripts and can in this way indirectly access all the WebExtension APIs.

Content scripts cannot directly access normal page scripts but can exchange messages with them using the standard window.postMessage() API.

Usually, when we talk about content scripts, we are referring to JavaScript, but you can inject CSS into web pages using the same mechanism.

See the content scripts article to learn more.

Web accessible resources 網頁無障礙資源

Web accessible resources are resources such as images, HTML, CSS, and JavaScript that you include in the extension and want to make accessible to content scripts and page scripts. Resources which are made web-accessible can be referenced by page scripts and content scripts using a special URI scheme.

For example, if a content script wants to insert some images into web pages, you could include them in the extension and make them web accessible. Then the content script could create and append img tags which reference the images via the src attribute.

To learn more, see the documentation for the web_accessible_resources manifest.json key.

 

 

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