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classes.js
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classes.js
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import { test, summary } from './helpers.js';
console.log('Class Tests\n');
class Person {
constructor(name, age) {
this.name = name;
this.age = age;
}
}
let person = new Person('Alice', 30);
test('constructor sets name', person.name, 'Alice');
test('constructor sets age', person.age, 30);
class Calculator {
constructor(value) {
this.value = value;
}
add(n) {
this.value = this.value + n;
return this.value;
}
subtract(n) {
this.value = this.value - n;
return this.value;
}
}
let calc = new Calculator(10);
test('method add', calc.add(5), 15);
test('method subtract', calc.subtract(3), 12);
class Point {
setCoords(x, y) {
this.x = x;
this.y = y;
}
getDistance() {
return this.x * this.x + this.y * this.y;
}
}
let p = new Point();
p.setCoords(3, 4);
test('no constructor class', p.getDistance(), 25);
class Counter {
constructor(start) {
this.count = start;
}
increment() {
this.count = this.count + 1;
return this.count;
}
}
let c1 = new Counter(0);
let c2 = new Counter(10);
test('instance isolation c1', c1.increment(), 1);
test('instance isolation c2', c2.increment(), 11);
test('typeof instance', typeof person, 'object');
test('instanceof Object', person instanceof Object, true);
class Rectangle {
constructor(width, height) {
this.width = width;
this.height = height;
}
area() {
return this.width * this.height;
}
}
let rect = new Rectangle(5, 10);
test('method uses props', rect.area(), 50);
rect.width = 8;
test('modified prop', rect.area(), 80);
let p2 = new Person('Charlie', 35);
delete p2.name;
test('delete property', p2.name, undefined);
test('other prop still exists', p2.age, 35);
class Chainable {
constructor(value) {
this.value = value;
}
add(n) {
this.value = this.value + n;
return this;
}
multiply(n) {
this.value = this.value * n;
return this;
}
get() {
return this.value;
}
}
let chain = new Chainable(5);
test('method chaining', chain.add(3).multiply(2).get(), 16);
class Feature {
constructor(name) {
this.name = name;
this.enabled = false;
}
enable() {
this.enabled = true;
}
disable() {
this.enabled = false;
}
}
let feature = new Feature('DarkMode');
test('initial bool prop', feature.enabled, false);
feature.enable();
test('toggle bool prop', feature.enabled, true);
class Animal {
constructor(name) {
this.name = name;
}
speak() {
return this.name + ' makes a sound';
}
}
class Dog extends Animal {
speak() {
return this.name + ' barks';
}
}
let dog = new Dog('Rex');
test('inheritance', dog.speak(), 'Rex barks');
test('instanceof parent', dog instanceof Animal, true);
test('instanceof child', dog instanceof Dog, true);
class Cat extends Animal {
speak() {
return super.speak() + ' - meow!';
}
}
let cat = new Cat('Whiskers');
test('super.method()', cat.speak(), 'Whiskers makes a sound - meow!');
class Bird extends Animal {
speak() {
let method = 'speak';
return super[method]() + ' - chirp!';
}
}
let bird = new Bird('Tweety');
test('super[method]()', bird.speak(), 'Tweety makes a sound - chirp!');
class Static {
static value = 42;
static method() {
return 'static';
}
}
test('static property', Static.value, 42);
test('static method', Static.method(), 'static');
class BankAccount {
#balance = 0;
constructor(initialBalance) {
this.#balance = initialBalance;
}
deposit(amount) {
this.#balance = this.#balance + amount;
return this.#balance;
}
withdraw(amount) {
this.#balance = this.#balance - amount;
return this.#balance;
}
getBalance() {
return this.#balance;
}
}
let account = new BankAccount(100);
test('private field initializer', account.getBalance(), 100);
test('private field deposit', account.deposit(50), 150);
test('private field withdraw', account.withdraw(30), 120);
class Vehicle {
#speed = 0;
constructor(initialSpeed) {
this.#speed = initialSpeed;
}
getSpeed() {
return this.#speed;
}
accelerate(amount) {
this.#speed = this.#speed + amount;
}
}
class Car extends Vehicle {
#model;
constructor(model, speed) {
super(speed);
this.#model = model;
}
getModel() {
return this.#model;
}
}
let car = new Car('Tesla', 0);
test('inherited private field', car.getSpeed(), 0);
car.accelerate(50);
test('inherited method with private field', car.getSpeed(), 50);
test('own private field', car.getModel(), 'Tesla');
class Accumulator {
count = 0;
increment() {
this.count = this.count + 1;
return this.count;
}
}
let accumulator = new Accumulator();
test('field initializer', accumulator.count, 0);
test('method with initialized field', accumulator.increment(), 1);
class Temperature {
#celsius = 0;
constructor(celsius) {
this.#celsius = celsius;
}
get fahrenheit() {
return (this.#celsius * 9) / 5 + 32;
}
set fahrenheit(f) {
this.#celsius = ((f - 32) * 5) / 9;
}
}
let temp = new Temperature(0);
test('getter', temp.fahrenheit, 32);
temp.fahrenheit = 212;
test('setter', Math.round(temp.fahrenheit), 212);
summary();

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classes.js (5 KB)

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