TypeScript · Generics and utility types

Generic constraint

Restricts a type parameter so the function can rely on certain members.

Syntax

<T extends { id: string }>

Example

function ids<T extends { id: string }>(items: T[]): string[] {
  return items.map(item => item.id);
}
console.log(ids([{ id: "a" }, { id: "b" }]));

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