How to reduce javascript object to only contain properties from interface

Question

When using typescript a declared interface could look like this:

interface MyInterface {
  test: string;
}

And an implementation with extra

Answer 1

In a general way, how can you make the 'reduced' variable to only contain the properties declared in the 'MyInterface' interface.

Since TypeScript is structural this means that anything that contains the relevant information is Type Compatible and therefore assignable.

That said, TypeScript 1.6 will get a concept called freshness. This will make it easier to catch clear typos (note freshness only applies to object literals):

// ERROR : `newText` does not exist on `MyInterface`
var reduced: MyInterface = {test: "hello", newTest: "world"};