总结
1、Pick
type MyPick<T, K extends keyof T> = {
[k in K]: T[k]
}
2、Readonly
type MyReadonly<T> = {
readonly [k in keyof T]: T[k]
}
3、tuple to object
type TupleToObject<T extends readonly (string | number)[]> = {
[k in T[number]]: k
}
注意: any要改成(string | number)
4、First
type First<T extends any[]> = T['length'] extends 0 ? never : T[0]
注意: ts中不能说 ===， 要用extends来代表，比如这里不能直接T['length'],或者写T['length'] === 0
5、tuple length
type Length<T extends readonly any[]> = T['length']
6、Exclude
type MyExclude<T, U> = T extends U ? never : T
7、Awaited
type MyAwaited<T extends Promise<any>> =
T extends Promise<infer U> ?
U extends Promise<infer K> ?
MyAwaited<Promise<K>>
: U
: never
8、If
type If<C extends boolean, T, F> = C extends true ? T : F
9、Concat
type Concat<T extends any[], U extends any[]> = [...T, ...U]
10、Includes (难度+)
type Equal<X, Y> = (<Res>() => Res extends X ? true : false) extends (<Res>() => Res extends Y ? true : false) ? true : false
type Includes<T extends readonly any[], U> =
T extends [infer First, ...infer Rest]
?
Equal<First, U> extends true
? true
: Includes<Rest, U>
:
false
11、Push
type Push<T extends any[], U> = [...T, U]
12、Unshift
type Unshift<T extends any[], U> = [U, ...T]
13、MyParameters
type MyParameters<T> = T extends (...args: infer a) => void ? a : []
