TypeScript 4.0 comes with lots of new features to make JavaScript development easier.

In this article, we’ll look at the best features of TypeScript 4.

• Variadic Tuples
• Labeled Tuple Elements
• Class Property Inference from Constructors
• Short-Circuiting Assignment Operators
• unknown on catch Clause Bindings

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Variadic Tuples

TypeScript 4.0 comes with data types for tuples with a variable number of elements.

We can use the spread operator to create a type with the elements we want in our tuple.

For example, we write:

type Strings = [string, string];
type Numbers = number[];

type Unbounded = [...Strings, ...Numbers, boolean];

to create an Unbounded data type to add a tuple type with strings, numbers, and booleans.

The inference process is also automatic so that if we have 2 strings, numbers, and a boolean in the same order, TypeScript will infer the tuple as having the Unbounded type.

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