源文件:

• contentscript.js
• manifest.json

manifast.json代码：

{"name": "Content Script Cross-Domain XMLHttpRequest Example","version": "2.0.0","description": "Demonstrates making cross domain requests from a content script by putting Twitter trends on Google News.","permissions": ["https://api.twitter.com/*"],"icons": {"48" : "sample-48.png","128" : "sample-128.png"},"content_scripts": [{"matches": ["http://news.google.com/*"],"js" : ["contentscript.js"]}]
}

contentscript.js代码：

/*
* Copyright (c) 2011 The Chromium Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*//*** Performs an XMLHttpRequest to Twitter's API to get trending topics.** @param callback Function If the response from fetching url has a*     HTTP status of 200, this function is called with a JSON decoded*     response.  Otherwise, this function is called with null.*/
function fetchTwitterFeed(callback) {var xhr = new XMLHttpRequest();xhr.onreadystatechange = function(data) {if (xhr.readyState == 4) {if (xhr.status == 200) {var data = JSON.parse(xhr.responseText);callback(data);} else {callback(null);}}}// Note that any URL fetched here must be matched by a permission in// the manifest.json file!var url = 'https://api.twitter.com/1/trends/daily.json?exclude=hashtags';xhr.open('GET', url, true);xhr.send();
};/*** Parses text from Twitter's API and generates a bar with trending topics at* the top of the current page** @param data Object JSON decoded response.  Null if the request failed.*/
function onText(data) {// Only render the bar if the data is parsed into a format we recognize.if (data.trends) {// Create the overlay at the top of the page and fill it with data.var trends_dom = document.createElement('div');var title_dom = document.createElement('strong');title_dom.innerText = 'Topics currently trending on Twitter:';trends_dom.appendChild(title_dom);for (var key in data.trends) {for (var i=0,trend; trend = data.trends[key][i]; i++) {var link_dom = document.createElement('a');link_dom.setAttribute('href', trend.url)link_dom.innerText = trend.name;link_dom.style.color = '#000';trends_dom.appendChild(document.createTextNode(' '));trends_dom.appendChild(link_dom);}break;}trends_dom.style.cssText = ['background-color: #ffd700;','background-image: -webkit-repeating-linear-gradient(' +'45deg, transparent, transparent 35px,' +'rgba(0,0,0,.1) 35px, rgba(0,0,0,.1) 70px);','color: #000;','padding: 10px;','font: 14px Arial;'].join(' ');document.body.style.cssText = 'position: relative';document.body.parentElement.insertBefore(trends_dom, document.body);}
};fetchTwitterFeed(onText);