Array<T> vs T[]

These two syntaxes are very similar, and are almost functionally identical in [[ts]]. The only real difference is the use of [[20210331123346-keyof-typescript]] operator.

type Person = {
  id: string;
  name: string;
};
 
const result: keyof Person[] = ["id", "name"];
// Type 'string[]' is not assignable to type 'keyof Person[]'.

The [] operator occurs before the keyof operator. Meaning it evaluates as keyof Person[], not ('id' | 'name')[]. You can fix this with parenthesis, or using the generic syntax.

const result: (keyof Person)[] = ["id", "name"];
const result: Array<keyof Person> = ["id", "name"];

They're so similar in fact, https://typescript-eslint.io/rules/array-type/ lets you pick one or the other for its rule.

https://www.totaltypescript.com/array-types-in-typescript

[[ts]]