Simon Willison’s Weblog

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707 posts tagged “javascript”

2013

Is there any alternative to devbootcamp.com or hackreactor.com in Europe?

http://www.makersacademy.com/ are running a similar program in the Old Street area of London.

Beginner JavaScript: more code or quality code?

Write more code. The more code you have written, the better you’ll be able to understand why certain techniques for creating higher quality code are worthwhile later on.

[... 70 words]

How do I choose between asynchronous web frameworks? My tech group is fairly language agnostic and we’re trying to standardize on some technologies.

Since they are all pretty close to each other and it sounds like your tech group’s skills would support any of them, I would suggest having your tram build a simple prototype in all three so you can compare them for your own particular team and situation.

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What are some JavaScript concepts that took you the longest to understand?

Closures, prototype inheritance, and the “this” keyword.

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What are the design mistakes in the Meteor framework?

Treating the non-JavaScript case as unimportant.

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How does a web page interact with a server to parse a dynamic JSON file?

If you’re only dealing with 60 records there’s no need to add a full database. I’ve actually hand coded a 50 record JSON file before and it was fine- use an editor with good JSON support (I like Sublime Text 2) and it’s pretty easy to hand write.

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How do I get started with node.js?

You don’t run Node.js in a script tag on your website. Node is a technology for writing servers in JavaScript—you can think of it as a replacement/alternative for PHP, Python, Ruby, ASP.NET etc.

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What are the strategies for a front end developer to keep up to date with the emerging technologies?

Step one: find developers who you respect and subscribe to their blogs, follow them on Twitter/Google+/etc and try to understand what they are talking about and what they think is exciting.

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Why is node.js so much faster?

There are two main reasons.

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2012

If I study HTML5, can I avoid having to learn javascript?

Many of the most exciting new features that fall under the term HTML5 only make sense in the context of JavaScript—things like Canvas, Web Workers, AppCache and so on. So no, you can’t learn HTML5 properly without getting familiar with JacaScript.

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Can you mark items on a website as ’unread’ without cookies?

It’s not very exciting, but CSS will let you set different styles for visited vs unvisited links and the technique has worked reliably since the mid 1990s.

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How difficult is to to learn a language framework, like node.js?

The answer varies enormously depending on the language and the framework. Some frameworks are very easy to pick up, others are harder.

[... 162 words]

What is a good cat name that relates to JavaScript?

I have two friends with cats that have names related to JavaScript. One is called “JavaScript” and the other is called “Widget”.

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Wouldn’t an ASCII cellular automaton in javascript be the simplest starting point to teach/learn programming?

Absolutely not. The first step in learning to program is understanding that a computer can be quickly made to do something useful by executing lines of code. Personally I’m a big fan of firing up something with an interactive prompt (like Python, or even Firebug or the Google Chrome JS console) and demonstrating that typing a line of code hitting return will get a useful response.

[... 87 words]

How do you change page content and URL without reloading the whole page?

This can only be done using JavaScript. You use XMLHttpRequest to pull in new information from the server (also known as Ajax—most people use a JavaScript library such as jQuery to handle this) and then use the HTML5 history API, in particular the pushState method, to update the URL.

[... 133 words]

How can I parse unquoted JSON with JavaScript?

Unquoted JSON isn’t JSON—the JSON spec requires that strings are quoted (with double quotes, not single quotes).

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Was CoffeeScript invented to help Ruby programmers get over that dirty yucky feeling they get when working in JavaScript?

The original Prototype JS library might fit that description—more than CoffeeScript, at any rate.

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How long until Ruby developers are as cheap as PHP developers? is it already happening? should I still learn it or it only has a couple years left and I’m better off with SSJS?

If you want to be a highly paid engineer, you should worry less about your expertise in a specific language and more about developing broad and deep skills across a wider range of development topics.

[... 197 words]

How is JSON different then a JavaScript (programming language) object?

JSON is a carefully selected subset of JavaScript. A JSON object can only consist of dictionaries, strings, numbers (in JavaScript floating point and integers are treated as the same thing), lists, booleans and null. The spec on JSON.org is a good guide: http://json.org/

[... 119 words]

Is there a method to programmatically clear browser cache in JavaScript?

No.

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Are there any performance drawbacks when rendering DOM views at runtime with JavaScript, rather than rendering server-sent HTML?

Yes, there is quite a significant impact on first-load performance. The browser has to pull down all of the linked scripts before it can display any content—if you’re using a library like jquery that’s a sizeable chuck of code that has to be loaded and executed just on its own.

[... 152 words]

2011

Does Quora use node.js?

Quora use their own event-based Python web framework which they’ve talked about quite a bit, called LiveNode. I believe it’s based on Tornado, the open source Python evented framework/appserver that was open sourced by Facebook after they acquired FriendFeed.

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Qwery—The Tiny Selector Engine. A quarter of the size of Sizzle (1K gzipped and minified) due to only supporting ID, class and attribute selectors. Could be useful for things like embeddable widgets and badges, where depending on a larger library is impolite.

# 2nd April 2011, 8:27 am / badges, css, javascript, recovered

Before events took this bad turn, the contract represented by a link was simple: “Here’s a string, send it off to a server and the server will figure out what it identifies and send you back a representation.” Now it’s along the lines of: “Here’s a string, save the hashbang, send the rest to the server, and rely on being able to run the code the server sends you to use the hashbang to generate the representation.” Do I need to explain why this is less robust and flexible? This is what we call “tight coupling” and I thought that anyone with a Computer Science degree ought to have been taught to avoid it.

Tim Bray

# 10th February 2011, 6 am / hashbanghell, javascript, urls, recovered, tim-bray

The code injected to steal passwords in Tunisia. Here’s the JavaScript that (presumably) the Tunisian government were injecting in to login pages that were served over HTTP.

# 24th January 2011, 6:45 pm / javascript, security, tunisia, recovered

Why would someone browse the web with JavaScript disabled?

Security conscious users (who understand the implications of XSS and CSRF attacks) sometimes disable JavaScript completely, or use a tool like the NoScript extension to disable it for all sites and only re-enable it on a small whitelist of sites that they trust.

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Display your events on your own website with Lanyrd Badges. We’ve launched badges for Lanyrd—JavaScript that lets you embed a top bar or a content “splat” showing events you plan to attend, talks you’ve given in the past and other various combinations. I’m quite pleased with the implementation—the badges are configured using classes on a link to your Lanyrd profile, and the badges themselves are served through a combination of Amazon CloudFront for the initial script and a Varnish cache for the badge data itself to keep things nice and snappy.

# 13th January 2011, 8:38 pm / badges, caching, cloudfront, javascript, lanyrd, varnish, recovered

Are there any wikis that allow the use of JavaScript on wiki pages?

Such a wiki would be grossly insecure. That said, take a look at TiddlyWiki—it’s implemented entirely in client-side JavaScript and allows plugins to be implemented by pasting JavaScript in to a textarea.

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Why does Facebook chat use subdomains so aggressively?

Probably because it involves long-running connections. Browsers have a limit on the number of connections you can have open to the same domain at the same time (I think it’s 8 in most browsers these days). If Facebook chat opened a connection to www.facebook.com and you opened up 8 Facebook windows you would no longer be able to navigate to any more Facebook pages, since all 8 connections would be taken up by the long lived chat connections. By connecting to a different subdomain for each connection this problem can be avoided.

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What are the reasons that make jQuery more popular than MooTools?

MooTools is the only major JavaScript library that still thinks extending the prototype of built-in JavaScript objects is a good idea.

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