Typescript: Overriding parent class properties in child

Question

Given the following case:

class Parent {
    propStr = "Hello";
    propNum = 42;

    constructor(propShared) {
        console.log(this.propStr); // Hello
        console.log(this.propNum); // 42
        console.log(propShared); // w/e
    }
}

class Child extends Parent {
    propStr = "Hi"; // overridden
    propNum = 1337; // overridden

    constructor(propShared) {
        super(propShared);
    }
}

let c = new Child("Foobar");

How do I make sure that the parent properties are properly overridden so that the console.log prints the child's properties?

Answer 1

Since you mentioned typescript, you can use a feature of typescript called Parameter Properties:

class Parent {
    constructor(public propStr = "Hello", public propNum = 42, public propShared: any) {
        console.log(this.propStr); // Hello
        console.log(this.propNum); // 42
        console.log(this.propShared); // w/e
    }
}

class Child extends Parent {
    constructor(propShared: any) {
        super("Hi", 1337, propShared);
    }
}

let c = new Child("Foobar");

The output will be exactly what you were expecting.