Manually making an HTTP requests in Node.js

This post will show how to make an HTTP request using the net module, rather than something more high-level like http or request . So we build on top of the existing TCP connection support. It turns out basic HTTP requests are pretty straightforward! ... more

Dynamic dataflow analysis for JavaScript: How FromJS 2 works

FromJS is a dynamic dataflow analysis tool for JavaScript. That means it collects data while your program is running, and can then use that data to answer questions about your program. ... more

V8 memory quiz

V8 is the JavaScript engine that Chrome and Node use to run JavaScript code. Take this quiz to discover some interesting implementation details about how V8 stores values in memory. ... more

How to write a JavaScript-free todo app using just HTML and CSS

I wrote a todo app. Unlike TodoMVC (where I took the design from) it doesn’t use JavaScript and instead all interactions are driven by CSS. ... more

Node-ChakraCore and the relationship between Node and V8

I’ve been looking at the ChakraCore source code recently, and I realized that before I didn’t have a good grasp of how JavaScript engines and browsers (or Node) actually relate to each other. ... more

A quick look at how Chrome's JavaScript code coverage feature works

There’s a new feature in Chrome Canary: JavaScript code coverage. It tells you how much of your code is actually executed, vs how much is loaded unnecessarily. ... more

Implementing a hash table in JavaScript

Hash tables are a common data structure for storing key-value pairs. ... more

Difference between Map and WeakMap in JavaScript

ES2015 introduced the new Map and WeakMap objects to JavaScript. They can be used as a key-value store, but unlike normal objects in JavaScript you can use objects as keys. Keys for normal objects ( {} ) always have to be strings, and if you try to use ... more

Lazy JavaScript Parsing in V8

JavaScript engines use a mechanism called lazy parsing to be able to run code more quickly. ... more

What's a statement completion value in JavaScript?

Paul Irish posted a question on Twitter yesterday. ... more

Time-travel debugging Node programs with Visual Studio Code

Microsoft are working on a time-travel debugger for JavaScript that allows you to step backward as well as forward. It’s currently in preview and won’t always work, but it’s really cool to play around with. ... more

Memoizing native JavaScript functions (or not)

Since JavaScript allows most native methods to be overwritten I was wondering if it’s possible to speed up an application by adding caching to native methods. ... more

How FromJS works

When inspecting a page with FromJS you can find the JavaScript code that’s responsible for a particular part of the UI. This article explains how that works. ... more

How much memory do JavaScript arrays take up in Chrome?

My code was using too much memory, so I had a look at how much memory a bunch of strings, objects, numbers and arrays take up. ... more

Resolving minified production stack traces with StackTrace.JS

JavaScript compilation and bundling tools usually output a source map file in addition to the compiled code. A debugging tool like Chrome DevTools can then use the source map to show you the code you wrote, rather than the compiled code that Chrome is ... more

Analyzing variable references with Tern

I recently built a Chrome extension that lets you jump to a variable’s definition when viewing JavaScript code on Github. ... more

Chrome DevTools: Never Pause Here

The “Never Pause Here” feature can prevent Chrome’s JavaScript debugger from pausing on the same line again and again. ... more

How do source maps work?

You’ve probably used a CSS generator like Sass or Less, or worked in a language like ES 2015 or CoffeeScript that is compiled to JavaScript code that the can run in the browser. ... more

JavaScript deep object comparison - JSON.stringify vs deepEqual

Checking if two JavaScript objects are equal to see if you need to update the UI is a common task in React. (Ideally you wouldn’t mutate your objects, but oh well.) ... more