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Partial<T>

将T的所有类型转换为可选类型，返回的类型可以为T的所有子集


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

type subTodo = Partial<Todo>

const todo1: subTodo = {
    title: 'This is a title'
}

const todo2: subTodo = {
    description: 'This is a description'
}

Required<T>

与Partial相反，将T的所有类型设为必选


interface Todo {
    title?: string;
    description?: string;
}

const todo1: Todo = {
    title: 'This is a title'
}

const todo2: Todo = {
    description: 'This is a description'
}

const todo3: Required<Todo> = { // 'description' is declared here.
    title: '123'
}

Readonly<T>

将T的所有类型设为只读


interface Todo {
		title: string;
}

const todo: Readonly<Todo> = {
		title: 'This is a title'
}

todo.title = 'new title' // Cannot assign to 'title' because it is a read-only property.

Record<K, T>

将一组属性K的类型设为T


interface Todo {
    title: string;
}

type TodoList = 'todo1' | 'todo2' 

const todos: Record<TodoList, Todo> = {
    todo1: { title: 'todo1' },
    todo2: { title: 'todo2' }
}

Pick<T, K>

从T中选出一组K构建出新类型


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

type TodoPreview = Pick<Todo, 'title' | 'done'> 

const todo: TodoPreview = {
    title: 'title',
    done: true
}

Omit<T, K>

从T中删除属性K，与Pick相反


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

type TodoPreview = Omit<Todo, 'description' | 'done'> 

const todo: TodoPreview = {
    title: 'title'
}

Exclude<T, U>

从联合T中排除U


type Todo = string | number | (() => void)

type TodoPreview = Exclude<Todo, string> 
// type TodoPreview = number | (() => void)

Extract<T, U>

与Exclude相反，从T中提取U相同的属性构建新的类型


type Todo = string | number | (() => void)

type TodoPreview = Extract<Todo, string> 
// type TodoPreview = string

NonNullable<T>

从T中剔除null和undefined类型


type Todo = NonNullable<number | string | null | undefined>
// tyoe Todo = <number | string>

Parameters<T>

从类型为T的函数的参数返回元祖类型Type


type T0 = Parameters<() => string>
// type T0 = []

type T1 = Parameters<(s: string) => void>
// type T1 = [s: string]

ConstructorParameters<T>

从构造函数类型的类型构造元组或数组类型。它产生一个包含所有参数类型的元组类型（或者never如果Type不是函数的类型）。


type T0 = ConstructorParameters<ErrorConstructor>;
// type T0 = [message?: string]

type T1 = ConstructorParameters<FunctionConstructor>;
// type T1 = string[]

type T2 = ConstructorParameters<RegExpConstructor>;
// type T2 = [pattern: string | RegExp, flags?: string]

type T3 = ConstructorParameters<any>;
// type T3 = unknown[]

ReturnType<T>

构造一个由 function 的返回类型组成的类型Type。


type T0 = ReturnType<() => string>
// type T0 = string

InstanceType<T>

返回构造函数类型T的实例类型


class C {
  x = 0;
  y = 0;
}

type T0 = InstanceType<typeof C>;  // C

type T1 = InstanceType<any>;  // any

type T2 = InstanceType<never>;  // any

TypeScript Utility Types