029.ReplaceKeys

实现一个类型 ReplaceKeys，用于替换联合类型中的键，如果某个类型没有此键，则跳过替换，类型需要三个参数

例如：

type NodeA = {
  type: "A"
  name: string
  flag: number
}
 
type NodeB = {
  type: "B"
  id: number
  flag: number
}
 
type NodeC = {
  type: "C"
  name: string
  flag: number
}
 
type Nodes = NodeA | NodeB | NodeC
 
type ReplacedNodes = ReplaceKeys<
  Nodes,
  "name" | "flag",
  { name: number; flag: string }
> // {type: 'A', name: number, flag: string} | {type: 'B', id: number, flag: string} | {type: 'C', name: number, flag: string} // would replace name from string to number, replace flag from number to string.
 
type ReplacedNotExistKeys = ReplaceKeys<Nodes, "name", { aa: number }> // {type: 'A', name: never, flag: number} | NodeB | {type: 'C', name: never, flag: number} // would replace name to never

答案

type ReplaceKeys<U, T, Y> = {
  [K in keyof U]: K extends T
    ? K extends keyof Y
      ? Y[K]
      : never
    : U[K]
}