What does the ampersand (&) mean in a TypeScript type definition?

Question

On line 60359 of this type definition file, there is the following declaration:

type ActivatedEventHandler = (ev: Windows.ApplicationModel.Activation.IActivatedEventArgs & WinRTEvent<any>) => void;

What does the & sigil mean in this context?

Answer 1

& in a type position means type intersection.

More

https://www.typescriptlang.org/docs/handbook/advanced-types.html#intersection-types

Answer 2

Typescript 中的交点类型

• 在类型上下文中的 TS 中的 & 表示交叉类型。
• 它将 2 个对象类型的所有属性合并在一起并创建一个新类型

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示例：

type dog = {age: number, woof: Function};
type cat = {age: number, meow: Function};

// Type weird is an intersection of cat and dog
// it needs to have all properties of them combined
type weird = dog & cat;

const weirdAnimal: weird = {age: 2, woof: () => {'woof'}, meow: () => {'meow'}}

interface extaprop {
    color: string
}

type catDog = weird & extaprop; // type now also has added color
const weirdAnimal2: catDog = {age: 2, woof: () => {'woof'}, meow: () => {'meow'}, color: 'red'}


// This is different form a union type
// The type below means either a cat OR a dog
type dogOrCat = dog | cat;