ES2020: Nullish coalescing for JavaScript
This blog post describes the ECMAScript feature proposal “Nullish coalescing for JavaScript” by Gabriel Isenberg. It proposes the ?? operator that replaces || when it comes to providing default values. Overview # The result of actualValue ?? defaultValue is: defaultValue if actualValue is undefined or null actualValue otherwise Examples: > undefined ?? 'default' 'default' > null ?? 'default' 'def
Working with stdout and stdin of a child process in Node.js
In this blog post, we run shell commands as child processes in Node.js. We then use async language features to read the stdouts of those processes and write to their stdins. Running commands in child processes # Let’s start with running a shell command in a child process: const {onExit} = require('@rauschma/stringio'); const {spawn} = require('child_process'); async function main() { const filePa
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
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
JavaScript: sparse arrays vs. dense arrays
In general, arrays in JavaScript are sparse – they can have holes in them, because an array is simply a map from indices to values. This blog post explains how to create dense arrays, arrays without holes. Sparse arrays Creating a sparse array of a given length is simple: > var a = new Array(3); > a [ , , ] > a.length 3 > a[0] undefined When you iterate over it, you can see that it has no elements
Asynchronous programming and continuation-passing style in JavaScript
Asynchronous programming and continuation-passing style in JavaScript In this blog post, we give a name to JavaScript’s callback-based asynchronous programming style: continuation-passing style (CPS). We explain how CPS works and give tips for using it. Asynchronous programming and callbacks If you have ever done asynchronous programming in JavaScript, you probably noticed that everything works di
Myth: JavaScript needs classes
Updates: [2012-03-17] I completely rewrote this post and changed its name (which previously was “JavaScript does not need classes”). [2012-07-29] Classes have been accepted for ECMAScript.next. [2012-10-03] Since this article has been written, it was decided that ECMAScript will have the special property __proto__ instead of the <| operator. [2013-10-21] Instead of the extension operator, ECMAScri
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Coding recipe: extracting loop functionality (via callbacks and generators)
What is JavaScript’s typeof operator used for?