In my Typescript code, I have 2 classes named A and B. Class B inherits from class A, where class A's constructor calls a function called init, and class B overrides the init function.
a.ts
export default class A {
constructor() {
this.init();
}
init() {
console.log("A.init()")
}
}
b.ts
import A from "./a"
export default class B extends A {
public bx = 3;
public by = 10;
public bz = 0;
constructor() {
super();
}
init(){
this.bx = 5;
this.bz = this.by;
console.log("B.init()")
}
}
When compiled with tsc, the resulting js files looked like this:
a.js
export default class A {
constructor() {
this.init();
}
init() {
console.log("A.init()");
}
}
b.js
import A from "./a";
export default class B extends A {
constructor() {
super();
this.bx = 3;
this.by = 10;
this.bz = 0; //even worse
}
init() {
this.bx = 5;
this.bz = this.by;
console.log("B.init()");
}
}
One might question why there is a line this.bx = 3; after super() in the constructor of b.js. It seems redundant since the property should already be initialized. This optimization could be handled better by the compiler to avoid unnecessary assignments.
Comparing to c# code:
using System;
public class Program
{
public static void Main()
{
B b = new B();
Console.Out.Write("x: " + b.x + " y: " + b.y);
}
}
class A {
public A() {
init();
}
public virtual void init() {
}
}
class B : A {
public int x = 3;
public int y = 10;
public int z = 4;
public B() : base() {
}
public override void init() {
this.x = 5;
this.y = this.z;
}
}
You will get x: 5 y: 4.