A JavaScript survival guide
Are you a programmer who is considering learning JavaScript, but unsure whether it is worth the pain? Then this blog post is for you: I argue that it is worth it and give tips for surviving the language. Why learn JavaScript? # The present # The main reason for choosing JavaScript is the breadth of its ecosystem: the web platform, Node.js, JSON, NoSQL databases, Cordova/PhoneGap, automating Phot
Multiple return values in ECMAScript 6
If you combine the features “property value shorthand” and “destructuring”, ECMAScript 6 gives you an elegant way to handle multiple return values. This blog post explains why that is useful and how it works. Destructuring # Destructuring is an ECMAScript 6 feature which lets you use patterns to extract values from an object: let obj = { first: 'Jane', last: 'Doe' }; let { first: f, last: l } = o
The ECMAScript 6 schedule changes
Allen Wirfs-Brock, editor of the ECMAScript 6 specification, recently mentioned on Twitter that the schedule for ECMAScript 6 has changed slightly. The changes # This is the content of Wirfs-Brock’s tweets: TC39 has decided to move the formal publication date of the ECMAScript 6 standard to June 2015. Work for ECMAScript 7 continues on schedule. The extra time is for more implementation feedback
ECMAScript 6’s new array methods
Check out my book (free online): “Exploring ES6”. Updated version of this blog post: chapter “New Array features”. This blog post explains what new array methods ECMAScript 6 will bring and how to use them in current browsers. Note: I’m using the terms constructor and class interchangeably. Class methods # Array has gained methods of its own. Array.from(arrayLike, mapFunc?, thisArg?) # Array.fro
Handling required parameters in ECMAScript 6
In ECMAScript 5, you have a few options for ensuring that a required parameter has been provided, all of which are somewhat brittle and inelegant: function foo(mustBeProvided) { if (arguments.length < 1) throw new Error(...) if (! (0 in arguments)) ... if (mustBeProvided === undefined) ... } In ECMAScript 6, you can (ab)use default parameter values to achieve more concise code (credit: idea by All
ECMAScript 6: TC39 meetings, March–November 2013
TC39 [1] is the committe that currently plans ECMAScript 6 (code-named ECMAScript.next), the next version of the JavaScript language standard. In this blog post, I’m summarizing the highlights of several meetings that they had in 2013, in March, May, July, September and November. Previous blog posts summarized prior meetings. This post is made possible by Rick Waldron’s excellent notes of the meet
JavaScript: single quotes or double quotes?
Today, I’ve asked on Twitter: JavaScript: single quotes versus double quotes. Any preferences? And I got great answers. Two funny examples: “Is this a ploy to get lots of @-replies?” – @tobie “Using single quotes saves bandwidth because you don’t have to send the extra pixels. #performance #truestory” – @mathias Among the respondents, there was a slight preference for single quotes. Examining the
Web platform: five technologies to look forward to in 2014
This blog post describes five technologies that will make 2014 an exciting year for the web platform: asm.js: near-native performance on the web ParallelJS: parallelized JavaScript code ECMAScript 6 (ES6): evolving the language, uniting the community Web Components: a standard infrastructure for widgets CSS Grid Layout: native-like GUI layout asm.js: near-native performance on the web What it is:
JavaScript gains support for SIMD
Update 2017-05-08: a proposal for SIMD.js has been rejected, in favor of providing similar functionality via WebAssembly. Recently, a new JavaScript feature has landed for the next Firefox Nightly: an API for SIMD (Single Instruction, Multiple Data). This blog post explains how the API works and how it fits into the JavaScript landscape. What is SIMD? SIMD is the ability of a CPU to apply an opera
Why are there so many array-like objects in the DOM?
Why are there so many array-like objects in the DOM? Tweet by Leon Arnott: #TIL the reason the DOM has so many "array-like objects" that aren't functional arrays… is because in Javascript 1.0, there were no arrays. Explanation: ECMAScript 1 does have arrays, but it corresponds to JavaScript 1.3. JavaScript version numbers apply to the JavaScript engines implemented by Netscape/Mozilla. The cross-e
The history of “typeof null”
Update 2013-11-05: I take a look at the C code of typeof to better explain why typeof null results in 'object'. In JavaScript, typeof null is 'object', which incorrectly suggests that null is an object (it isn’t, it’s a primitive value, consult my blog post on categorizing values for details). This is a bug and one that unfortunately can’t be fixed, because it would break existing code. Let’s expl
The JavaScript console API
In most JavaScript engines, there is a global object console with methods for logging and debugging. That object is not part of the language proper, but has become a de facto standard, since being pioneered by the Firebug debugger. Since their main purpose is debugging, the console methods will most frequently be used during development and rarely in deployed code. This blog post gives an overview
Tips for using window in JavaScript
In web browsers, window refers to an object that contains the global variables. This blog post explains how it works and when to use it. The global object and window The ECMAScript specification uses the internal data structure environment to store variables. The language has the somewhat unusual feature of making the environment for global variables accessible as an object, the so-called global o
Unicode and JavaScript
Update 2013-09-29: New sections 4.1 (“Matching any code unit”) and 4.2 (“Libraries”). This blog post is a brief introduction to Unicode and how it is handled in JavaScript. History Unicode was started in 1987, by Joe Becker (Xerox), Lee Collins (Apple) and Mark Davis (Apple). The idea was to create a universal character set, as there were many incompatible standards for encoding plain text at that
The ECMAScript Internationalization API
The ECMAScript Internationalization API is a standard JavaScript API that helps with tasks related to internationalization: collation, number formatting, date and time formatting. This blog post gives a brief overview and points to more reading material. The ECMAScript Internationalization API, edition 1 The first edition of the API provides the following services: Collation. supports two scenario
Protecting objects in JavaScript
This blog post is a quick refresher of how objects can be protected in JavaScript. There are three levels of protection: Preventing extensions is the weakest level, sealing is stronger, freezing is strongest. Preventing extension Object.preventExtensions(obj) makes it impossible to add properties to obj. Example: var obj = { foo: 'a' }; Object.preventExtensions(obj); Now adding a propert fails sil
Callable entities in ECMAScript 6
Update 2013-11-28: There won’t be generator arrow functions in ECMAScript 6 (details). In ECMAScript 5, one creates all callable entities via functions. ECMAScript 6 has more constructs for doing so. This blog post describes them. The status quo: ECMAScript 5 In ECMAScript 5, functions do triple duty: As normal functions: you can directly call functions. As methods: you can assign a function to th
A meta style guide for JavaScript
JavaScript has many great style guides. Thus, there is no need to write yet another one. Instead, this blog post describes commonly accepted meta style rules and conventions that I like that are controversial. The idea is to help you make a more informed decision about what is right for you. Existing style guides The two style guides I like best are: Idiomatic.js: Principles of Writing Consistent,
Directories for JavaScript resources
I recently asked on Twitter whether people knew any good directories for JavaScript libraries and got several good answers. I was only aware of the following two directories: “JSDB: a collection of the best JavaScript libraries” “Microjs: fantastic micro-frameworks and micro-libraries for fun and profit” More directories: “JavaScriptOO: every JavaScript project you should be looking into” (via @ge
In defense of JavaScript’s constructors
JavaScript’s constructors have never been particularly popular: Douglas Crockford doesn’t like them and recently, more anti-constructor material has been published (two examples: blog posts by Kyle Simpson and Eric Elliott). In this blog post, I explain that not all of the constructors’ flaws are real. But even with those that are real, I still recommend to use them. I’ll tell you why and what the
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