基本格式

{
    "manifest_version": 2,
    "name": "My Extension",
    "description": "Extension description",
    "version": "1.0",
    "permissions": [
        "tabs"
    ]
}

content_script

content_script是植入型的，它会被植入到符合匹配的网站页面上。在页面加载完成后执行。content_script最有用的地方是操作网站页面上的DOM。一切平时做前端的一些操作它都可以做，像什么添加、修改、删除DOM，获取DOM值，监听事件等等，都可以很容易的做到。

使用方式：

{
    "manifest_version": 2,
    "name": "My Extension",
    "description": "Extension description",
    "version": "1.0",

    "content_scripts": {
        "js": [
            "content.js"
        ],
        "css": ["style.css"],
        "matches": ["http://*.jgb.cn/*","http://*.amazon.com/*","https://*.amazon.com/*"]
    }
}

background_script

它在chrome扩展启动的时候就启动了，做着它的事，而且等待着你给他的指令。 它没办法控制页面元素，但可以通过content_script告诉它。 ajax同理，如果要在页面打开时向别的服务器请求数据，这时就可以告诉background_script，让它去请求，然后把返回的数据发送给content_script。这样就不会受到浏览器的安全限制影响。

使用方式

{
    "manifest_version": 2,
    "name": "My Extension",
    "description": "Extension description",
    "version": "1.0",

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

跨域

默认情况下Ajax是不允许跨域的，但扩展提供了跨域的配置。

{
    "permissions": [
        "http://www.jgb.cn/" // 允许跨域访问www.jgb.cn
    ]
}

Sending a request from a content script looks like this:

chrome.runtime.sendMessage({greeting: "hello"}, function(response) {
  console.log(response.farewell);
});

Sending a request from the extension to a content script looks very similar, except that you need to specify which tab to send it to. This example demonstrates sending a message to the content script in the selected tab.

chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {
  chrome.tabs.sendMessage(tabs[0].id, {greeting: "hello"}, function(response) {
    console.log(response.farewell);
  });
});

On the receiving end

chrome.runtime.onMessage.addListener(
  function(request, sender, sendResponse) {
    console.log(sender.tab ?
                "from a content script:" + sender.tab.url :
                "from the extension");
    if (request.greeting == "hello")
      sendResponse({farewell: "goodbye"});
  });

官方文档

localStorage

操作

// 存储/修改
localStorage.name = 'only';
localStorage['name'] = 'only';

// 删除
localStorage['name'] = null; 删除一个
localStorage.clear(); 删除所有

// 查
var name = localStorage.name;
var name = localStorage['name'];