如何在 typescript 中的 object 中的 select 属性

Question

How can I select object property depending on what is passed to the function as a second argument?

interface Type{
  first:string;
  second:string;
}

function foo(args:Type,key:string) {
  console.log(args.key)//if key=="first" select args.first, if key=="second" select args.second
}

foo({first:"hi",second:"man"},"first")

Answer 1

You can write it like this: args[key]

Answer 2

A better way of doing this is to restrict the second argument to that of the available keys that are available on the object itself, such as:

function foo(args: Type, key: keyof Type) {
    console.log(args[key]);
}

Then call the method:

foo({ first: "hi", second: "man" }, "first")

The following results in an error:

foo({ first: "hi", second: "man" }, "somethingElse")