Model Window depending on the environment in TypeScript

localhost-window.ts

enum Hostname {
    IPv4 = 'localhost',
    IPv4Default = '127.0.0.0/8',
    IPv6 = '[::1]',
}

const isLocalhost = (window: Window): window is Window.Localhost => (
    window.location.hostname === 'localhost' ||
    window.location.hostname === '[::1]' ||
    /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/.test(window.location.hostname)
)

declare namespace Window {
    interface Localhost extends Window {
    location: Window['location'] & { hostname: Hostname };
    __DEVTOOLS__: boolean;
    }
}

function assert(condition: boolean): asserts condition {
    if (!condition) {
        throw new Error()
    }
}

/**
 * If you expect this module to be executed ONLY in development
 */
assert(isLocalhost(window));

window.__DEVTOOLS__;