background 编辑

An Array of Strings, each of which is a path to a JavaScript source. The path is relative to the manifest.json file itself. These are the scripts which will be executed in the extension's background page.

The scripts share the same window global context.

The scripts are loaded in the order they appear in the array.

If you specify a value for scripts, then an empty page will be created in which your scripts are run.

Note: If you want to fetch a script from a remote location with the <script> tag (e.g. <script src = "https://code.jquery.com/jquery-1.7.1.min.js">), you will also have to change the content_security_policy key in the manifest.json file of your extension.

Note: In Firefox prior to version 50, when the debugger is open, scripts are not always loaded in the order given in the array. To work around this bug, you can use the page property and include background scripts from the page using <script> tags. This bug is fixed in Firefox 50. From that point on, scripts are always loaded in the order given in the array.

If you need some particular content in the page, you can define your own page using the page property, which is a String representing a path, relative your manifest.json file, to an HTML document included in your extension bundle.

If you use this property, you can not specify background scripts using scripts, but you can  include your own scripts from the page, just like in a normal web page.

A Boolean value.

• true indicates the background page is to be kept in memory from when the extension is loaded or the browser starts until the extension is unloaded or disabled, or the browser is closed (i.e. the background page is persistent).
• false indicates the background page may be unloaded from memory when idle and recreated when needed. Such background pages are often called Event Pages, because they are loaded into memory to allow the background page to handle the events to which it has added listeners. Registration of listeners is persistent when the page is unloaded from memory, but other values are not persistent. If you want to store data persistently in an event page, then you should use the storage API.