10.2 Roads Module (Eloquent JavaScript Solutions)

10-2 Eloquent Javascript Solutions.js

const {buildGraph} = require("./graph");

const roads = [
  "Alice's House-Bob's House",   "Alice's House-Cabin",
  "Alice's House-Post Office",   "Bob's House-Town Hall",
  "Daria's House-Ernie's House", "Daria's House-Town Hall",
  "Ernie's House-Grete's House", "Grete's House-Farm",
  "Grete's House-Shop",          "Marketplace-Farm",
  "Marketplace-Post Office",     "Marketplace-Shop",
  "Marketplace-Town Hall",       "Shop-Town Hall"
];

function splitRoads(r) {
  let newRoads = [];
  for (let roadPair of r) {
    newRoads.push(roadPair.split('-'));
  }
  return newRoads;
}

exports.roadGraph = buildGraph(splitRoads(roads));

// a better solution is to use a map:
// exports.roadGraph = buildGraph(roads.map(r => r.split("-")));

Modules

10.2 Road Module

Write a CommonJS module, based on the example from Chapter 7, which contains the array of roads and exports the graph data structure representing them as roadGraph. It should depend on a module ./graph, which exports a function buildGraph that is used to build the graph. This function expects an array of two-element arrays (the start and end points of the roads).

Hints

Since this is a CommonJS module, you have to use require to import the graph module. That was described as exporting a buildGraph function, which you can pick out of its interface object with a destructuring const declaration.

To export roadGraph, you add a property to the exports object. Because buildGraph takes a data structure that doesn’t precisely match roads, the splitting of the road strings must happen in your module.