Typescript conversion to boolean

In Typescript I can do this:

var xxx : some_type;

if (xxx)
    foo();
else
    bar();

Here xxx will be treated as a boolean, regardless of its type.

I would like to do the same thing in a function argument. I have this function:

function foo(b : boolean) { ... }

I want to be able to call foo(xxx) and have xxx treated as a boolean, regardless of its type. But Typescript won't allow that.

I tried this:

foo(<boolean>xxx);

but that Typescript won't allow that either.

I can do this:

foo(xxx ? true : false);

But that seems a bit silly. Is there a better way to do it?

Solution

You can use double exclamation sign trick which Typescript does allow and which works fine in JavaScript:

foo(!!xxx);

Alternatively, cast it to any

foo(<any>xxx);