✔️ Simple type annotated flow example

flow-example.js

// @flow
import type {KnockoutComputed, KnockoutObservable} from 'knockout';
import ko from 'knockout';

interface FooJSON {
    name: string;
    surname: string;
}

interface FooModel {
    name: KnockoutObservable<string>;
    surname: KnockoutObservable<string>;
    fullName: KnockoutComputed<string>;
}

type FooFactory = (input: FooJSON) => FooModel;

const fooFactory: FooFactory = payload => {
    const name = ko.observable(payload.name);
    const surname = ko.observable(payload.surname);

    return {
        name,
        surname,
        fullName: ko.pureComputed(() => {
            return `${name()} ${surname()}`;
        })
    };
};

export default fooFactory;

Ah, this will be amazing :)