The official announcement says: “We are pleased to announce the availability of TypeScript 3.4! TypeScript 3.4 introduces a new mark called -cremental that tells TypeScript to save the project’s graphical information from the last compilation. Incremental will use this information to find the least costly way to check and make changes to your project, Daniel wrote in a blog post. ”
Here are five new features added to TypeScript 3.4.
1. Incremental flag
TypeScript saves the information on the project graph of the latest compilation. TypeScript has been able to reduce the size of Visual Studio Code to subsequent compilations of a project to about one fifth of the original.
2. Higher order type inference from generic functions
When inferring type arguments, TypeScript propagates the type parameters of generic function arguments to the type of function obtained.
3. ReadonlyArray and readonly tuples
The new version makes it easy to use read-only array types. It also acts as a syntax for ReadonlyArray. Any variable that references ReadonlyArray can not add, delete, or replace any element in the array.
4. Const Assertions
The new assertion favour immutability in the types inferred for literal expressions.
5. Type-checking for globalThis
The new addition aims to provide a standard way to access the global scope, used in different environments.