Primitives and arrays

You know string, number and boolean. An array of them gets [] after the type: number[] is a list of numbers, any length.

There's a second spelling that means exactly the same: the generic form Array<T>. Pick one style per project.

TypeScript infers arrays too. [1, 2, 3] becomes number[], and a mixed literal like ["axe", 3] becomes (string | number)[]: every element may be either.

let ids: number[] = [1, 2, 3];
let names: Array<string> = ["Brunn", "Hilde"];
let mixed: (string | number)[] = ["axe", 3];
let split: string[] | number[] = [1, 2]; // all strings OR all numbers

• Mind the brackets: (string | number)[] allows mixing, string[] | number[] doesn't.
• There's no separate integer or float type: 3 and 3.5 are both number.