Web Apps

In this post, I’m going to take a close look at how JavaScript’s prototypal inheritance works by analysing how Microsoft’s TypeScript language uses it to provide a simple implementation of classes. Don’t worry if you’ve never used TypeScript, we’re not really concerned with the language itself here, just the JavaScript that is produced by its compiler, and how it achieves class-based inheritance in a language that doesn’t natively support it.

This is of particular importance because EcmaScript 6 will include classes that work a lot like TypeScript’s. The idea of adding classes to JavaScript is controversial, but I think some of the hostility stems from a mistaken belief that classes are some kind of competing inheritance mechanism to prototyping, or are an attempt to turn JavaScript into Java. In fact, modern proposals for classes in JavaScript are just a syntactic codification of prototypal inheritance patterns that are already in use.