Chrome extension to allow lookup of books in Amazon and Fishpond

bookup.js

// Copyright (c) 2013 Bennett McElwee. All rights reserved.
// This is a Chrome extension.

// The onClicked callback function.
function onClickHandler(info, tab) {
  // console.log("Info: " + JSON.stringify(info));
	if (info.menuItemId == "bookup-amazon-to-fishpond") {
		var isbn = getAmazonIsbn(info.pageUrl);
		chrome.tabs.update(tab.id, {url: getFishpondUrl(isbn)});
	} else if (info.menuItemId == "bookup-fishpond-to-amazon") {
		var isbn = getFishpondIsbn(info.pageUrl);
		chrome.tabs.update(tab.id, {url: getAmazonUrl(isbn)});
	} else if (info.menuItemId == "bookup-amazon") {
		var isbn = info.selectionText.trim();
		chrome.tabs.update(tab.id, {url: getFishpondUrl(isbn)});
	} else if (info.menuItemId == "bookup-fishpond") {
		var isbn = info.selectionText.trim();
		chrome.tabs.update(tab.id, {url: getFishpondUrl(isbn)});
	}
};
chrome.contextMenus.onClicked.addListener(onClickHandler);

function getFishpondUrl(isbn) {
	return "http://www.fishpond.co.nz/advanced_search_result.php?isbn=" + isbn;
}
function getAmazonUrl(isbn) {
	return "http://www.amazon.com/gp/product/" + isbn;
}
function getAmazonIsbn(url) {
	var match = url.match(/\/gp\/product\/(\d+)/);
	return match ? match[1] : '';
}
function getFishpondIsbn(url) {
	var match = url.match(/.*\/(\d+)\/?$/);
	return match ? match[1] : '';
}

// Set up context menu tree at install time.
chrome.runtime.onInstalled.addListener(function() {

//    chrome.contextMenus.create({
//		"documentUrlPatterns": ["*://*.fishpond.co.nz/Books/*"],
//		"title": "Look up this book on Amazon",
//		"contexts":["page"],
//		"id": "bookup-fishpond-to-amazon"
//		});
    chrome.contextMenus.create({
		"documentUrlPatterns": ["*://*.amazon.com/gp/product/*"],
		"title": "Look up this book on Fishpond",
		"contexts":["page"],
		"id": "bookup-amazon-to-fishpond"
		});
    chrome.contextMenus.create({
		"title": "Look up %s on Amazon",
		"contexts":["selection"],
		"id": "bookup-amazon"
		});
    chrome.contextMenus.create({
		"title": "Look up %s on Fishpond",
		"contexts":["selection"],
		"id": "bookup-fishpond"
		});
});

manifest.json

{
  "name": "Bookup",
  "description": "Look up a book",
  "version": "0.1",
  "permissions": ["contextMenus"],
  "background": {
    "persistent": false,
    "scripts": ["bookup.js"]
  },
  "manifest_version": 2
}