卡在 javascript 中的 object inheritance

Question

I'm trying to understand the object inheritance in js by building a base constructor and working through that but its not working for me. I have gone wrong somewhere in my code:

function car(make, model, transmission) {
    this.make = make;
    this.model = model;
    this.transmission = transmission;
    this.report = function() {
        return ("make " + this.make + "model " + model);
    }

}

function SUV(make, model, transmission, mpg) {
    this.mpg = mpg;
    this.carInfo = car;
    this.carInfo = (make, model, transmission);

}
SUV.prototype = new Car();
SUV.prototype.getMPG = function() {
    return "the suv mpg is" + this.mpg;
}
mySuv = new Suv("nissan", "almera", "manual", 12);
document.writeIn(newSuv + report());

Answer 1

You do not inherit just by assigning the parent class to an instance method (which you immediately overwrite anyway).

Instead, you must call the parent constructor on this :

function SUV(...) {
    car.call(this, ...);
    ....
}

call allows you to specify what this will refer to in the parent method. car.call(this, ...) is equivalent to:

this.car_funk = car
this.car_funk(...);
delete this.car_funk;`

Or this:

car.bind(this)(...)