Typescript Utility Types Cheatsheet

interface Todo {
	id: number;
	text: string;
	due: Date
}

type TodoKeys = keyof Todo; // "id" | "text" | "due"

interface Person {
    name: string;
    age: number;
}
type Partial<T> = {
    [P in keyof T]?: T[P]; // P will be each key of T
}
type PersonPartial = Partial<Person>; // same as { name?: string;  age?: number; }

type Props = { req: number; reqUndef: number | undefined; opt?: string; };

type Props = PickByValue<Props, number | undefined>; // { req: number; reqUndef: number | undefined }

type Person = {name: string, nickName: string};

type OptionalPerson = Partial<Person>; // {name?: string, nickName?: string}

interface Todo {
    title: string;
    description: string;
    completed: boolean;
}

type TodoPreview = Pick<Todo, 'title' | 'completed'>;

const todo: TodoPreview = {
    title: 'Clean room',
    completed: false,
};

interface Todo {
    title: string;
    description: string;
    completed: boolean;
}

type TodoPreview = Omit<Todo, 'description'>;

const todo: TodoPreview = {
    title: 'Clean room',
    completed: false,
};

type T0 = Exclude<"a" | "b" | "c", "a">;  // "b" | "c"
type T1 = Exclude<"a" | "b" | "c", "a" | "b">;  // "c"
type T2 = Exclude<string | number | (() => void), Function>;  // string | number

type T0 = Extract<"a" | "b" | "c", "a" | "f">; // "a"
type T1 = Extract<"a" | "b" | "c", "a" | "b">; // "a" | "b"
type T2 = Extract<string | number | (() => void), Function>; // () => void