JavaScript and TypeScript are inextricably tied together. Thus, while this chapter covers two technologies, ECMAScript and TypeScript, they are similar enough for this chapter to cover both simultaneously. How similar are they to each other? Well, for the most part, you can consider TypeScript to be a superset of JavaScript. The most useful description of their relationship is the following: TypeScript is a strictly typed language with lot of powerful features with optional typing, and with its transpiler, it becomes plain JavaScript. This is important and brings several advantages for developers; it's compelling enough for Google's Angular team to switch from JavaScript to TypeScript for developing Angular itself. We'll cover what a transpiler is, as well as what the advantages of using TypeScript are, very shortly.