When Microsoft announced the new programming language TypeScript for web, nobody expected anything huge. Several notable companies have had similar ambitions, and did fail (for example Google with Dart).
Today, TypeScript is nevertheless very relevant. This is because of a trait that the developers of the WWW neglected, but is very important in the corporate world: type security. With TypeScript you might develop a bit slower than with other languages, but the resulting code is much less prone to errors, and thus more durable. Big companies that previously used the programming language Java because of these problems, are now switching to TypeScript and its available frameworks (for example Angular) for new web based projects.