gistfile1.js

// import libraries
jetpack.future.import("menu");
jetpack.future.import("selection");

// create a new menu item
jetpack.menu.context.page.add({
    label: "TranslateIt!",
    command: function() { TranslateIt(); }
});

// do translate
function TranslateIt() {
    var url = 'http://ajax.googleapis.com/ajax/services/language/translate?v=1.0' 
            + '&langpair=|zh-TW'
            + '&q=' + escape(jetpack.selection.text);
    $.getJSON(url, function(result) {
        if (result.responseStatus == 200) {
            jetpack.notifications.show(result.responseData.translatedText);
        }
    });
};