A way to add a Firefox toolbar button with the addons SDK

toolbar-button.js

/** Hat tip to <http://stackoverflow.com/questions/5572632/> */
var data = require("self").data;
var {Cc, Ci} = require("chrome");
var mediator = Cc['@mozilla.org/appshell/window-mediator;1'].getService(Ci.nsIWindowMediator);


/**
 * Add a toolbar button to the main nav bar.
 * 
 * options you may want to set:
 * image, label, click
   * use use tabs.activeTab.attach() in the click handler to execute scripts in
   * the context of the browser tab
 */
function addToolbarButton(options) {
    var document = mediator.getMostRecentWindow("navigator:browser").document;      
    var navBar = document.getElementById("nav-bar");
    if (!navBar) return; // s.o.l.
    var btn = document.createElement("toolbarbutton");  

    var defaults = {
        type: 'button',
        class: 'toolbarbutton-1',
        orient: 'horizontal'
    };

    // Set attributes and click event handler
    for (var o in options) {
        if o == 'click' {
            btn.addEventListener('click', options[o], false);
        } else {
            btn.setAttribute(o, options[o]);
        }
    }

    // Set fallback attributes
    for (var d in defaults) {
        if (d not in options) {
            btn.setAttribute(d, defaults[d]);
        }
    }
    navBar.appendChild(btn);
}

exports.addToolbarButton = addToolbarButton;