【20日目】TypeScriptのUtility Typesを読む②

type ParamsType = Parameters<(a:string,b:number)=>any>

const param:ParamsType = [
    "string",
    1
]

const list: [number, string, boolean] = tuple();

const fn = () => "string"

type FnReturnType = ReturnType<typeof fn> // type FnReturnType = string

class a {
}

type b = InstanceType<typeof a>

const c:b = new a()

type UpperCaseType = Uppercase<"a" | "b" | "c"> // UpperCaseType = "A" | "B" | "C"

type CapitalizeType = Capitalize<"aaa" | "bbb" | "ccc"> // CapitalizeType = "Aaa" | "Bbb" | "Ccc"

type user = {
    Name: string,
    Age: number
}

type UserKeys = Uncapitalize<keyof user> // UserKeys = "name" | "age"