never类型

• TypeScript never 类型
• never 尤雨溪

高级类型

高级类型
TypeScript 高级类型清单（附 demo）

联合类型与extends的区别

Difference between extending and intersecting interfaces in TypeScript?

in

function showType(arg: FirstType | SecondType) {
    if ('x' in arg) {
        console.log(`The property ${arg.x} exists`);
        return `The property ${arg.x} exists`;
    }
    throw new Error('This type is not expected');
}