Suggestion: use typescript and shared message type definitions.

[edeykholt]

Typescript will avoid some errors.

Suggest somewhere the message type definitions for those between a webpage and an ContentScript injected by an extension are defined in a separate .ts. Something like the following example:

// Message types from page to content script
const PAGE_EVENT_TYPE = Object.freeze({
SELECT_IDENTIFIER: "select-identifier",
SELECT_CREDENTIAL: "select-credential",
SELECT_ID_CRED: "select-aid-or-credential",
SELECT_AUTO_SIGNIN: "select-auto-signin",
NONE: "none",
VENDOR_INFO: "vendor-info",
FETCH_RESOURCE: "fetch-resource",
AUTO_SIGNIN_SIG: "auto-signin-sig",
SIGNIFY_EXTENSION: "signify-extension"
})

// Message types from content script to page
const PAGE_POST_TYPE = Object.freeze({
SIGNIFY_EXT: "signify-extension",
SELECT_AUTO_SIGNIN: "select-auto-signin",
SIGNIFY_SIGNATURE: "signify-signature"
})

// interfaces for the messages posted to the web page
interface ICsPageMsg {
type: any
version: string
}

interface ICsPageSignifyExtensionMsg extends ICsPageMsg {
type: typeof PAGE_POST_TYPE.SIGNIFY_EXT;
version: "0.0.1"
data: {
extensionId: string;
};
}
...
With these, a browser extension developer then can import these definition and use the ones it needs.
A webpage developer can import and use the ones it needs.