Typescript: declare variable with same type as another

Question

Is there any way to declare a variable with the type of another variable? For instance, I declare a class member with some type, and then later I want to declare another variable in a function of the same type. But I don't want to modify the original declaration, and don't want to duplicate it. It seems like you should be able to do something like:

class Foo {
    bar: {[key: string]: string[]};

    func() {
        const x: TypeOf<Foo.bar> = {};
        ....
    }
}

I've heard of something like this specifically for return types of functions, but I can't find it anymore...

Answer 1

You can use typeof but in class you should get to property:

class Foo {
    bar: {[key: string]: string[]};

    func() {
        const x: typeof Foo.prototype.bar = {};
        // here x has type `{[key: string]: string[]}`
    }
}

And another example outside of class:

class A {
    b: string = ''
}

type test = typeof A.prototype.b // type is `string`

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