Simon Willison’s Weblog

571 items tagged “javascript”

Why do browsers allow cross-domain JavaScript to execute but not XMLHttpRequests?

It’s called the Same Origin Policy, and it’s principally about intranets. Imagine you have a URL http://intranet.corp/top-secret-...—and you then visit http://evil.example.com/ . If cross domain XHR was allowed the evil site could suck that secret document off your intranet without you realising.

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Porting Flickr to YUI 3: Lessons in Performance (at YUIConf 2010). Some very interesting tips here. The new Flickr photo pages suffered from what I’ve been calling “Flash of Un-Behavioured Content”, where slow loading JavaScript results in poor behaviour from some UI controls. They started using “Action Queueing”, where a small JS stub ensures a loading indicator is shown for clicks on features that have not yet fully loaded. Also, it turns out some corporate firewalls (Sonicwall in particular) dislike URLs over 1600 characters, and filter out any URL with xxx in it. # 10th November 2010, 6:33 pm

What is the best JS library for automated cropping?

Not entirely clear what you’re looking for, but if you mean a UI tool for letting people resize and crop an image Jcrop is really nice http://deepliquid.com/content/Jc...

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jQuery 1.4.3 Released. Once again, the thing that impresses me most about this jQuery release is how stable the core API is. Hardly any new methods added, but the existing methods are made faster, more flexible and more predictable. The same as been true for the past several releases as well. It just keeps getting more and more polished. # 17th October 2010, 12:15 am

Why do some websites implement their logout link as a form post via JavaScript versus a plain old GET request?

Probably because if you implement logout as a GET action, I can force you to log out of a site by tricking you in to visiting a page with an <img src="http://yoursite.com/logout/" width="1" height="1"> element on it.

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JS had to “look like Java” only less so, be Java’s dumb kid brother or boy-hostage sidekick. Plus, I had to be done in ten days or something worse than JS would have happened.

Brendan Eich # 16th October 2010, 8:25 am

Annotated backbone.js. Literate programming. # 13th October 2010, 5:24 pm

Backbone.js. As should be expected for a DocumentCloud project, Backbone is a concise, elegant and educational take on the JavaScript MVC pattern. Depends on Underscore.js and plays well with jQuery. # 13th October 2010, 5:23 pm

What companies are using Node.js in production in Texas?

There’s a list on this page: https://github.com/joyent/node/w...

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Why don’t more people use Google Web Toolkit for web development as opposed to scripting alternatives like JavaScript?

I’m morally opposed to GWT, because I don’t believe in building sites or applications that are entirely dependent on JavaScript to function. As someone who took the time to learn JavaScript, I’m also not at all convinced that Java is a more productive language.

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Why do so few companies use the Dojo Toolkit?

Dojo is fantastic software, but it does a lot more than the other libraries and consequently has a much higher learning curve. It’s advanced features may serve as something of a disadvantage for achieving more widespread adoption—most developers don’t need the more advanced abstractions provided by Dojo when they start their projects, and by the time they DO need that stuff they’ve already written a ton of code using another library!

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PaintbrushJS. Impressive open source JavaScript library from Dave Shea for applying image filters (sharpen, blur, emboss, greyscale etc) to the canvas element. # 9th October 2010, 11:53 am

Is there a modern, tested, reliable, standalone onDomReady function that isn’t part of a larger library?

I’ve just noticed that the original comment thread on Dean Edwards blog from 2006 is still open, and a comment by byron from January 2010 has a promising looking candidate: http://dean.edwards.name/weblog/...

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Why are XSS attacks spreading like fire these days?

XSS attacks are common and easy, and crop up all the time. What’s new is that the number of people who are aware of the potential for XSS worms has increased hugely, so when an XSS does crop up in something popular there’s a much higher chance of someone turning it in to a worm (as happened with Twitter the other day).

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The Web for me is still URLs and HTML. I don’t want a Web which can only be understood by running a JavaScript interpreter against it.

Me, on Twitter # 27th September 2010, 4:37 pm

What is the largest production deployment of Server Side JavaScript?

I believe Flickr used to use Rhino for scripting the image processing (resizing, thumbnailing, sharpening) that was applied to every single uploaded photo. No idea if that’s still the case though.

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Why do some people disable JavaScript in their browser?

For security reasons.

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10K Apart Contest: Cheating by Compressing Your JavaScript and CSS to PNG Images. Fascinating hack: transform your JS and CSS in to coloured pixels, save the result as a PNG to benefit from PNG’s built in compression algorithms, then read the data back out of the PNG and convert it back to text using JavaScript and canvas—all to reduce the on-disk filesize when entering the 10K app competition. Alex’s GithubFinder entry is worth checking out too. # 23rd August 2010, 9:45 am

Polymaps. Absurdly classy: “a JavaScript library for image- and vector-tiled maps using SVG”. It can pull in image tiles from sources such as OpenStreetMap, then overlay SVG paths specified using GeoJSON. The demos make use of GeoJSON tiles for US states and counties hosted on AppEngine. The library is developed by Stamen and SimpleGeo, and released under a BSD license. SVG support in the browser is required. # 20th August 2010, 6:46 pm

Closure Compiler Service (via) A hosted version of the Google Closure Compiler (JavaScript minifier) running on App Engine. It has both a user interface and a REST API, which means you can use it as part of an automated build process without needing to set up a local copy of the software. # 9th August 2010, 1:17 pm

Hookbox (via) For most web projects, I believe implementing any real-time comet features on a separate stack from the rest of the application makes sense—keep using Rails, Django or PHP for the bulk of the application logic, and offload any WebSocket or Comet requests to a separate stack built on top of something like Node.js, Twisted, EventMachine or Jetty. Hookbox is the best example of that philosophy I’ve yet seen—it’s a Comet server that makes WebHook requests back to your regular application stack to check if a user has permission to publish or subscribe to a given channel. “The key insight is that all application development with hookbox happens either in JavaScript or in the native language of the web application itself”. # 29th July 2010, 9:48 am

canto.js: An Improved HTML5 Canvas API (via) Improved is an understatement: canto adds jQuery-style method chaining, the ability to multiple coordinates to e.g. lineTo at once, relative coordinate methods (regular Canvas does everything in terms of absolute coordinates), the ability to use degrees instead of radians, a rounded corner shortcut, a more convenient .revert() method and a simple parser that can understand SVG path expressions! The only catch: it uses getters and setters so won’t work in IE. # 29th July 2010, 9:39 am

nodejitsu’s node-http-proxy (via) Exactly what I’ve been waiting for—a robust HTTP proxy library for Node that makes it trivial to proxy requests to a backend with custom proxy behaviour added in JavaScript. The example app adds an artificial delay to every request to simulate a slow connection, but other exciting potential use cases could include rate limiting, API key restriction, logging, load balancing, lint testing and more besides. # 28th July 2010, 11:34 pm

Multi-node: Concurrent NodeJS HTTP Server. Kris Zyp’s library for spawning multiple Node child processes (one per core is suggested) for concurrent request handling, taking advantage of Node’s child_process module. This alleviates the need to run multiple Node instances behind an nginx load balancer in order to take advantage of multiple cores. # 15th July 2010, 8:22 am

DNode: Asynchronous Remote Method Invocation for Node.js and the Browser. Mind-bendingly clever. DNode lets you expose a JavaScript function so that it can be called from another machine using a simple JSON-based network protocol. That’s relatively straight-forward... but DNode is designed for asynchronous environments, and so also lets you pass callback functions which will be translated in to references and used to make remote method invocations back to your original client. And to top it off, there’s a browser client library so you can perform the same trick over a WebSocket between a browser and a server. # 11th July 2010, 2:27 pm

Diffable: only download the deltas. JavaScript library for detecting and serving diffs to JavaScript rather than downloading large scripts every time a few lines of code are changed. “Using Diffable has reduced page load times in Google Maps by more than 1200 milliseconds (~25%). Note that this benefit only affects users that have an older version of the script in cache. For Google Maps that’s 20-25% of users.” # 11th July 2010, 12:19 pm

getlatlon.com commit dae961a... I’ve finally added an OpenStreetMap tab to getlatlon.com—here’s the diff, it turns out adding a custom OpenStreetMap layer to an existing Google Maps application only takes a few lines of boilerplate code. # 10th July 2010, 12:22 pm

Escaping regular expression characters in JavaScript (updated). The JavaScript regular expression meta-character escaping code I posted back in 2006 has some serious flaws—I’ve just posted an update to the original post. # 4th July 2010, 6:23 pm

jQuery.queueFn. “Execute any jQuery method or arbitrary function in the animation queue”. I’m surprised this isn’t baked in to jQuery itself—the plugin is only a few lines of code. # 30th June 2010, 12:59 pm

pdf.js. A JavaScript library for creating simple PDF files. Works (flakily) in your browser using a data:URI hack, but is also compatible with server-side JavaScript implementations such as Node.js. # 17th June 2010, 7:39 pm