Recently I wrote an article about de-structuring in TypeScript, and hinted that Kotlin has a similar feature, but in more of a “strongly typed” language style.

A fairly recent addition to Typescript is index types and the keyof operator.

ECMAScript is all about wrangling loosely typed variables.

When learning a language built on another existing platform, like TypeScript (or, for that matter Kotlin), one of the challenges you face is understanding the underlying platform or language so that you can, in turn, understand how the higher-level language is applied to meet the restrictions and features of the lower-level language.

Kotlin has an annotation called @JvmDefault which, like most of the “Jvm” prefixed annotations, exists to help massage the Kotlin compiler output to match Java classes in a certain way. This annotation was added in 1.2.40, and has now seen some experimental enhancements in 1.2.50, so it seems worth exploring what this is all about.