introtype.ts

Typescript Intro to Types solution

interface Foo{
  twittle: string;
  doBarStuff(b: Bar): number;
  fooOptional?: number
}

interface Bar{
  one: number;
  two: string;
}

let foo: Foo = {
  twittle: 'abc',
  doBarStuff: (bar) => { return bar.one + bar.two.length },
  fooOptional: 123
}

let bar = {
  one: 10,
  two: 'hello world'
}

let fooKeyStore: { [index: string]: Foo } = {}
fooKeyStore['firstFoo'] = foo;
fooKeyStore['secondFoo'] = {
    twittle: 'dcf',
    doBarStuff: (bar) => { return bar.one / bar.two.length }
}

let bars = [
  bar,
  {
    one: 20,
    two: 'hello universe'
  }
]

function fooBar(foo: Foo, bars: Bar[]) {
  let barsTotal = 0;
  bars.forEach(bar => {
    barsTotal += foo.twittle.length + foo.doBarStuff(bar);
  });
  return barsTotal;
}

fooBar(fooKeyStore['secondFoo'], bars);