flow-type + immutable-js

cta.js

/* @flow */

var T = require('immutable');

type Branch    = T.List<string>
type TrainLine = T.Map<string, Branch>
type CTAMap    = T.Map<string, TrainLine>

/*
 * Representation of Chicago's train stops and branches
 */

var ctaMap: CTAMap = new T.Map();

var blueLine: TrainLine = new T.Map().set("O'Hare Branch",
  T.List.of(
    "O'Hare",
    "Rosemont",
    "Cumberland",
    "Harlem",
    "Jefferson Park",
    "Montrose",
    "Irving Park",
    "Addison",
    "Belmont",
    "Logan Square",
    "California",
    "Western",
    "Damen"
  )
).set("Milwaulkee-Dearborn Subway",
  T.List.of(
    "Division",
    "Chicago",
    "Grand",
    "Clark / Lake",
    "Washington",
    "Monroe",
    "Jackson",
    "LaSalle",
    "Clinton"
  )
).set("Forest Park 'Congress' Branch",
  T.List.of(
    "UIC-Halsted",
    "Racine",
    "Illinois Medical Center",
    "Western",
    "Kedzie-Homan",
    "Pulaski",
    "Cicero",
    "Austin",
    "Oak Park",
    "Harlem",
    "Forest Park"
  )
);

ctaMap = ctaMap.set('blue', blueLine);

// ERROR: call of method count
//        Method cannot be called on optional of Branch
var numStops: number = blueLine.toSeq().reduce((r, n) => r + n.count(), 0);

// ERROR: call of method count
//        Method cannot be called on optional of Branch
var numStopsByBranch = blueLine.map((v, k) => v.count());

console.log("The CTA Blue Line has " + numStops + " stops.")
// => The CTA Blue Line has 33 stops.

console.log(numStopsByBranch);
// => Map { O'Hare Branch: 13, Milwaulkee-Dearborn Subway: 9, Forest Park 'Congress' Branch: 11 }