Use array map to modify entire object

Question

I'm using typescript (angular2) to create a "reset" method on an object array:

cars [
  {
    id: 1,
    color: white,
    brand: Ford,
    model: Mustang,
    ...
  }, 
  ... 
]

User can modify this objects, and he can also "reset" to default values. So I keep an array of objects called originalCars. So if he selects the first object and choose "reset", I want to do something like: car = originalCar.

I was doing this:

this.selectedCars().map(car=> {
  const originalCar = this.getOriginalCar(car.id);
  car.color = originalCar.color;
  car.brand = originalCar.brand;
  // ... I'm doing this to all properties of my object
 });

This is working, but I want to do it simple. Something like car = originalCar. I tried:

this.selectedCars().map(car=> {
  const originalCar = this.getOriginalCar(car.id);
  return originalCar;
  // also tried car = originalCar;
 });

The selectedCars method is:

selectedCars = () => {
    return this.cars.filter(car=> {
        return car.selected;
    });
};

But It did not work. How can I do this?

Poul Kruijt · Accepted Answer · 2020-09-14 12:32:34Z

With the map function you create a new array of whatever thing you return from the method. Which means, you have to overwrite the selectedCars property:

this.selectedCars = this.selectedCars.map(car => this.getOriginalCar(car.id));

A more weird way of doing it, is by using the forEach method. That would be something like this:

this.selectedCars.forEach((car, index) => {
  this.selectedCars[index] = this.getOriginalCar(car.id);
});

If you just want to reset one car by id:

resetCar(id: number): void {
  const idx = this.selectedCars.findIndex((car) => car.id === id);

  if (idx > -1) {
    this.selectedCars[idx] = this.getOriginalCar(id);
  }
}

New information has come to light, and your selectedCars() is a method. In that case you can do the following:

this.selectedCars().forEach((car, index) => {
  Object.assign(car, this.getOriginalCar(car.id));
});

_{It however does not feel proper, because you are updating an object and causing side-effects. Better would be to just create a new array/object collection}

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