Question

169

Create empty object or object with null values for already known keys

rated 0 times [ 176] [ 7] / answers: 1 / hits: 36172 / 9 Years ago, sun, november 15, 2015, 12:00:00

I am playing around with JavaScript and AngularJS since a few days and I am not sure about the following:

I am working on a sample project in which a user is able to create a new car with just a few properties stored in an JS object like this:

var car = {

    color: 'black',

    seating: 'leather',

    fuelconsumption: 'moderate'

}

The user can create a new car by clicking on an add-button. Angular then creates a new instance of a car and the user can specify the wishes for new car.

However, should I create an empty object like

var car = {}

and add the needed keys using the bound text inputs or should I do something different?

Since the properties of a new car are known a-priori I could also create an object with the needed keys and null as their values like this:

var car = {

    color: null,

    seating: null,

    fuelconsumption: null

}

Which way would be more preferable due to e.g. best-practise?

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kaley

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3 Years ago

answered 9 Years ago collinisaaka · Accepted Answer

In Javascript, there is often not a need to initialize a property to null. This is because referencing a property that has not been initialized just harmlessly returns undefined which can work just as well as null. This is obviously different than some other languages (Java, C++) where properties of an object must be declared before you can reference them in any way.

What I would think might make sense in your case is to create a constructor function for creating a car object because you will presumably be creating more than one car and all possible car objects won't be known at the time you write the code. So, you create a constructor function like this:

function Car(color, seating, fuel) {

    this.color = color;

    this.seating = seating;

    this.fuelConsumption = fuel;

}

Then, you can create a new Car object like this:

var c = new Car('black', 'leather', 'moderate');

console.log(c.color);   // 'black'