【TS 类型操作之 keyof】

keyof

const myObj = {
  a: 1,
  b: 2,
  c: 3,
}
const objKeys = <Obj>(obj: Obj): (keyof Obj)[] => {
  return Object.keys(obj) as (keyof Obj)[]
}
objKeys(myObj).map((el) => el)
Object.keys(myObj).map((el) => el)

function getFromObject<MyOBject, Key extends keyof MyOBject>(
  myObject: MyOBject,
  myKey: Key
): MyOBject[Key] {
  return {} as any
}
let result: number = getFromObject(myObj, 'c')