Typescript casting object's property

Question

I\'m working with indexeddb and typescript. My issue is that TS doesn\'t seem to be able handle the event.target.result property. Case in point:

req         


        

Answer 1

You can also cast using the 'as' keyword like this

interface MyCustomUserInterface {
    _id: string;
    name: string;
}

const userID = (req.user as MyCustomUserInterface)._id
...

Cheers!

Answer 2

If you are looking for a oneliner you can cast it by adding some extra parenthesis like so:

indexedDB.open("test", 1).onsuccess = (ev) => {
    var result: IDBDatabase = (<IDBOpenDBRequest>ev.target).result;
}

Also notice the : IDBDatabase because result is typed as any in the Typescript definition file. It isn't needed but using it as an "any" type would mean no typechecking by the compiler.

Now you can use the result like you want with the methods available as defined here: http://www.w3.org/TR/IndexedDB/#database-interface