Typescript not triggering errors for an uninitialized object property named "name"

Question

I've found some weird behavior on a Typescript code that I'm writing.

Typescript playground link

Somehow Typescript does not trigger an error for an not initialized property if that property name is name :

What is this? Is this a bug or what?

This is the error for the value property:

No value exists in scope for the shorthand property 'value'. Either declare one or provide an initializer.(18004)

interface INTERFACE_A {
    name: string,               // ALSO TRIED WITH OTHER TYPES. SAME RESULT
}

function fooA(x: INTERFACE_A): INTERFACE_A { return x; }

fooA({
    name                        // THIS SHOULD BE AN ERROR (BUT IT'S NOT)
});

const objA: INTERFACE_A = {
    name                        // THIS SHOULD BE AN ERROR (BUT IT'S NOT)
}

interface INTERFACE_B {
    value: string
}

function fooB(x: INTERFACE_B): INTERFACE_B { return x; }

fooB({
    value                       // THIS IS AN ERROR (OK)
});

const objB: INTERFACE_B = {
    value                       // THIS IS AN ERROR (OK)
}

This doesn't seem to be related to the Typescript Playground, since it's also happening in my VSCode dev environment:

UPDATE:

This is probably related to the window.name property, which is of type string . But it still behaves differently than window.innerWidth , for example:

See that TS complains if I use innerWidth as a string , but it does not complain when I try to use window.name as a number :

Typescript playground link

Answer 1

{ name } is shorthand for { name: name } , window.name is built-in property, and properties of window are global in browsers, so name is a global property that's equivalent to window.name .

In effect, your code is doing this:

fooA({
  name: window.name
})

and that's totally valid (although probably not what you wanted).

Answer 2

For a solution to this kind of error, ESLint can be configured to give errors when you use browser globals like name without an explicit reference to the window object ( window.name )

1. Install ESLint
2. Install ESLint and it for typescript code ( instructions here )
3. install the no-restricted-globals package
4. Add this to your rules in .eslintrc.js :

module.exports = {
  // ... other fields omitted
  rules: {
    // ... other rules omitted
    "no-restricted-globals": ["error"].concat(
      require("confusing-browser-globals")
    ),
  },
}