Recently, I created a JavaScript library named jsandbox. jsandbox is used for evaluating JavaScript code safely in a sandbox. jsandbox uses web worker threads to do this.
The API for using the jsandbox library is described in detail and with an example on the project page.
I have created a very simple Jetpack feature called GTranslatifier that adds a 
icon to Firefox’s status bar for easy access to Google Translate services. Upon clicking the icon, one of the following things happen. If no text is selected in the tab currently being viewed, the page in the browser tab currently being viewed is translated into your native language. If the icon was left-clicked, the translated page will be loaded in the same tab. If the icon was middle-clicked or right-clicked the translated page is loaded in a new tab. If there is text selected in the current tab being viewed, a new tab is opened which has a translation of the selected text. If you are on a page translated using Google Translate, clicking the button will return you to the original page.
I have created a library that implements every array method for XML lists in JavaScript. The methods output XML as opposed to arrays to make the output directly usable with other XML. To get the array representation of an XML list, use slice. This returns XML when used to slice out ranges from XML but if no arguments are passed or a third argument is specified which is equivalent to true, it will convert an XML list to an array instead. For example, xmllist.slice(3, 5) returns an XML list and xmllist.slice(3, 5, true) returns an array.
You can download the Array methods for XML lists JavaScript library at code.eligrey.com/xml-array-methods/. If you wish to minify the library yourself, make sure that your minification tool supports the E4X used in this library. Rhino-based minifiers fail, throwing syntax errors, and /packer/ errantly minifies all of the public methods names preceded by .function::.
The following example demonstrate the usefulness of having array methods for XML lists. If you want to try out the example in a JavaScript shell, make sure XML.prettyPrinting is set to false, which removes any unnecessary whitespace from xml.toString() and xml.toXMLString().
var foo = <></>; // XMLList literal foo.push(<n>0</n>, 1, 5, 3, 2, 6, 4); foo.toXMLString() === "<n>0</n><n>1</n><n>5</n><n>3</n><n>2</n><n>6</n><n>4</n>"; foo = foo.sort(function(a, b) { return a - b; }); foo.toXMLString() === "<n>0</n><n>1</n><n>2</n><n>3</n><n>4</n><n>5</n><n>6</n>"; foo.filter(function(x) { // filter out integers less then 3 if (!(x < 3)) return true; }).toXMLString() === "<n>3</n><n>4</n><n>5</n><n>6</n>"; foo.slice(2, 5).toXMLString() === "<n>2</n><n>3</n><n>4</n>"; foo.splice(2, 1, <n>9</n>, <n>8</n>).toXMLString() === "<n>2</n>"; foo.slice(2, 5).toXMLString() === "<n>3</n><n>9</n><n>8</n>"; foo.pop().toXMLString() === "<n>6</n>"; foo.shift().toXMLString() === "<n>0</n>"; foo.shift().toXMLString() === "<n>1</n>"; foo.unshift(<bar/>); foo.toXMLString() === "<bar/><n>3</n><n>9</n><n>8</n><n>4</n><n>5</n>"; foo.map(parseFloat).forEach(function(n){ print(n) }) // prints NaN, 3, 9, 8, 4, 5 foo.some(function(x) { // some are greater than 5 if (x > 5) return true; }) === true; foo.every(function(x) { // all are numbers if (typeof x == "number") return true }) === false;
I have created a Jetpack feature called Edit Page to see what developing a Jetpack feature would be like. As the name implies, it lets you edit any web page in one click. Right clicking on the Edit Page button added to the status bar toggles spellcheck. To change the default spellcheck preference for the Jetpack feature, go to about:config and search for the jetpacks.editpage.spellcheck boolean preference to toggle it. The following is the code I used to implement version 0.1 of the Jetpack feature:
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Mozilla Labs’ latest creation, Jetpack, is a great way to extend Firefox. It currently has a poorly documented API that doesn’t mention all of the public methods and fields. Due to Mozilla Labs’ decision of not putting the API documentation on MDC or the MozillaWiki, I cannot update the documentation myself. Therefore, I will list all of Jetpack’s documented and undocumented features as of version 0.1.2 in this blog post.
You can’t do things like jetpack.tabs.focused.contentWindow.foo = "bar". I find this much too restrictive, as it hinders a developer’s ability to make an API for a webpage to communicate with a jetpack to do things that need more privileges. Ironically, it seems that jetpacks have full access to Firefox’s XPCOM (Components.*, ect.) which means, with a little hacking, it may be possible to bypass this restriction. The follow code shows an example of getting an nsIAlertsService and using it instead of jetpack.notifications.show.
var body = "Some text", title = "Notification", icon = "http://code.eligrey.com/favicon.ico", classObj = Components.classes['@mozilla.org/alerts-service;1'], alertService = classObj.getService(Components.interfaces.nsIAlertsService); alertService.showAlertNotification(icon, title, body);