All examples were tested against TypeScript 2.8.3 with strictNullChecks and strictFunctionTypes turned on. The original intent of this article was to explain how we can write a type Equ<A, B> that proves that A and B are equal. Spoiler alert: it's not really possible in a sound way in TypeScript…

All the code in this article has been tested with typescript 2.7.2 Sometimes, the base types offered by TypeScript, like number or string, are not enough to express precisely what you want. For example, you may want to represent the age of a user with a type indicating that it…

All the code of this article has been tested with typescript 2.6.1 TypeScript compilation can sometimes yield unexpected results. Take the following code snippet, for example: Why does userList compile and not user? …

All the code here was tested with TypeScript 2.2.2 TypeScript offers native enumerations with an implementation that makes it an alias of number. An example of such an enumeration could be: There are some problems with the above code: If we add an element in our enum (eg. BLUE)…

All the code present in this article was tested with TypeScript 2.2.1 and Lodash 4.6.1 The emergence of static type checking in JavaScript has put an end to the dynamic programming approach. If you had the following snippet in your JavaScript for it to work in TypeScript, the only…