What does the `is` keyword do in typescript?

Question

I came across some code that looks like this:

export function foo(arg: string): arg is MyType {
    return ...
}

I haven\'t been able to se

Answer 1

The only use I know is the one of your example: specifying a "type predicate" (arg is MyType) in an user defined Type Guard

See User Defined Type Guards in this reference

Here is another reference