Multiple type signatures for members, Union Types in TypeScript

Question

If I have a property that might be a string or a boolean how do I define it:

interface Foo{
    bar:string;
    bar:boolean;
}

I don\'t want

Answer 1

As of 2015, union-types work:

interface Foo {
    bar:string|boolean;
}

Answer 2

This is usually referred to as "union types". The TypeScript type system from 1.4 does allow for this.

See: Advanced Types

Answer 3

Not saying this answers your question, but could you resort to something like this?

interface Foo<T>{
    bar:T;
}

function createFoo<T>(bar:T) : Foo<T>{
    return {bar:bar};
}

var sFoo = createFoo("s");
var len = sFoo.bar.length;

var bFoo = createFoo(true);
var result = bFoo.bar === true;