Advanced Game Design with HTML5 and JavaScript

Chapter 1. Level Up!

Some New JavaScript Tricks

Getting Loopy with Arrays

Using forEach

let planets = ["jupiter", "venus", "saturn", "mars"];
planets.forEach(planet => console.log(planet));

Using a for of Loop

for (let planet of planets) {
  console.log(planet);
}

//An *array comprehension*
let numbers = [1, 2, 3, 4, 5];
let squared = [for (x of numbers) x * x];

Looping through Objects

Object.keys(room).forEach((key) => {
  let value = room[key];
  console.log("key: " + key + ", value: " + value);
});

//Or the same thing with a good old-fashioned for in loop
for(let key in room) {
  if(room.hasOwnProperty(key)) {
    let value = room[key];
    console.log("key: " + key + ", value: " + value);
  }
}

Looping through Only Some Array Elements

let instruments = ["guitar", "piano", "tabla", "ocarina", "tabla"];
let found = instruments.some(instrument => instrument === "tabla");
if (found) console.log("tabla found!");

Finding Array Elements

let found = instruments.find(x => x === "tabla");
console.log(found);
//Displays: tabla

let index = instruments.findIndex(x => x === "tabla");
console.log(index);
//Displays: 2

Mapping an Old Array to a New Array

let words = ["fun", "boring", "exciting"];
let betterWords = words.map(x => x + "ish");

Filtering Elements from an Array

let numbers = [11, 43, 9, 112, 64, 312, 92];
numbers = numbers.filter(x => x < 100);

Reducing Array Elements to a Single Value

let numbers = [73, 19, 2, 144, 43, 7];
total = numbers.reduce((a, b) => a + b);
console.log(total);

Making Variables from Arrays with Destructuring

let statistics = [16, 170, 10];
let [age, height, grade] = statistics;
console.log(`Age: ${age} Height: ${height} Grade: ${grade}`);

Creating Objects

Making Objects from Other Objects

Configuring Objects

function animal(config) {
  //Create the animal template
  let newObject = {
    legs: 4,
    eyes: 2,
    say: "Huh?",
    speak() {
      console.log(this.say);
    }
  };
  //Copy the config object's properties onto the animal
  Object.assign(newObject, config);
  //Return the newObject
  return newObject;
}

//Make a cat, and change the "say" value
let cat = animal({
  say: "Meow!",
  fur: "black"
});

cat.speak();
console.log(Object.keys(cat))

//Displays:
//Meow!
//["legs", "eyes", "say", "speak", "fur"]