Before the lab

• Read Eloquent JavaScript Chapter 7.

Background

• The first half of the lab references Eloquent JavaScript Chapter 4.

• The second half of this lab lab is based on Chapter 7 of Eloquent JavasScript.

• You will also need ES2015 classes, which were introduced in L10

Discussion

• Questions about Assignment 3?
• Questions about Lab 10?

Deep Comparison

Follow the Deep Comparison Exercise to write a function deepEqual that passes the following tests. Jasmine uses something very similar for the toEqual matcher used below. Coming from Racket this is a bit disappointing, since the built in equal? function can already do these kinds of comparisons.

describe("equal", function () {
    let obj = {here: {is: "an"}, object: 2};
    it("self", function () {
        expect(deepEqual(obj,obj)).toBe(true);
    });
    it("null", function () {
        expect(deepEqual(null,null)).toBe(true);
    });

    it("different", function () {
        expect(deepEqual(obj, {here: 1, object: 2})).toBe(false);
    });
    it("equivalent", function () {
        expect(deepEqual(obj, {here: {is: "an"}, object: 2})).toBe(true);
    });
});

Variadic Functions

Traditional JavaScript supports the arguments object, which is something like an array of all the arguments passed to the function.

function makemap (){
    let map={};
    if (arguments.length %2 != 0)
        return map;

    for (let i=0; i<arguments.length; i+=2) {

    }

    return map;

}

ES2015 supports rest arguments similar to those in Racket. These are more general than the arguments object, and generally preferred.

function brag(name,...args){
    console.log(name + " has");
    for (let i=0; i<args.length; i++) {
        console.log("\t"+args[i]);
    }
}

ES2015 also supports default values for function parameters

function win(person,thing="a brick"){
    console.log(person + " won " + thing);
}

Robot I: Representing a graph

• Make a directory ~/fcshome/cs2613/labs/L11

• Create a file ~/fcshome/cs2613/labs/L11/village.js, and copy the code from Meadowfield

  • For your journal: what is const?

• run jasmine init in that directory to create an appropriate jasmine configuration.

• export roadGraph from village.js and add a suite (i.e. describe) of two tests to spec/village.spec.js

  • Check that the destinations adjacent to "Alice's House" are ["Bob's House","Cabin","Post Office"]. Make sure your test still passes if the order of adjacent places changes.
  • use jasmine.objectContaining to check that the list of places adjacent to "Alice's House" contains "Bob's House".

Robot II: Representing State

• Copy the class VillageState from Eloquent JavaScript

• Convert the following code from Eloquent JavaScript to tests in jasmine/village.spec.js

let first = new VillageState(
  "Post Office",
  [{place: "Post Office", address: "Alice's House"}]
);
let next = first.move("Alice's House");
console.log(next.place);
// → Alice's House
console.log(next.parcels);
// → []
console.log(first.place);
// → Post Office

Use a new suite (describe) labelled "VillageState".

• For your journal:
  • what property of the VillageState data stucture is emphasized in this section of the book?
  • what "update" operation(s) in Racket does this remind you of?

Before you leave

• Make sure all of your work related to the delivery Robot is committed and pushed before you go. We will continue working with this example next lab.