Microsoft today announced the release of TypeScript 4.0. This is a major release with no breaking changes. It comes with improved performance and scalability, new features like variadic tuple types, labeled tuple elements and more.

What’s new in TypeScript 4.0:

• Variadic Tuple Types
• Labeled Tuple Elements
• Class Property Inference from Constructors
• Short-Circuiting Assignment Operators
• unknown on catch Clauses
• Custom JSX Factories
• Speed Improvements in build mode with --noEmitOnError
• --incremental with --noEmit
• Editor Improvements
  • Convert to Optional Chaining
  • /** @deprecated */ Support
  • Partial Semantic Mode at Startup
  • Smarter Auto-Imports

You can learn about the above features in detail from the source link below.

Source: Microsoft