Kevin Powell - Community•2y ago

Understanding object notation - JS newbie

A third installment of my non-understanding of JS, but hey ... here we go. As mentioned before I'm taking codecademy's intro course, and today it's all about objects. This one slide is about nested objects, and the text says: "In application code, objects are often nested— an object might have another object as a property which in turn could have a property that’s an array of even more objects!" And then this code is showned as an example:

const spaceship = {
     telescope: {
        yearBuilt: 2018,
        model: '91031-XLT',
        focalLength: 2032 
     },
    crew: {
        captain: { 
            name: 'Sandra', 
            degree: 'Computer Engineering', 
            encourageTeam() { console.log('We got this!') } 
         }
    },
};

const spaceship = {
     telescope: {
        yearBuilt: 2018,
        model: '91031-XLT',
        focalLength: 2032 
     },
    crew: {
        captain: { 
            name: 'Sandra', 
            degree: 'Computer Engineering', 
            encourageTeam() { console.log('We got this!') } 
         }
    },
};

I get confused, because I assume they mean that captain is an object within crew, but isn't it really a property within a property? Isn't the only object in this code spaceship?

11 Replies

Jochem•2y ago

the outer object spaceship has a property called crew. That property's value is an object, with a property called captain. The value of captain is another object crew's value could also be a string, number, boolean, or function type, but in this case it's an object

13eck•2y ago

In your code there are ~~three~~four objects: 1) The value of spaceship is an object 2) The value of spaceship.telescope is an object 3) The value of spaceship.crew is an object 4) The value of spaceship.crew.captain You'll find in JS that objects are ubiquitous (found everywhere) and are the defaults for a lot of data structures

Jochem•2y ago

value of captain too

Å Marlon GOP•2y ago

Hi again @jochemm ! Are you enjoying this as much as I am! 🤣 ... and hi to you too Beck! When you say value, do you mean everything within the {}, or do you mean e.g. yearBuilt: 2018 in telescope only.

13eck•2y ago

I get confused, because I assume they mean that captain is an object within crew, but isn't it really a property within a property? Isn't the only object in this code spaceship?

Objects have property names (like telescope is a property name on the spaceship object) as well as a value. As an example, the telescope object has a property of yearBuilt with a value of 2018.

Å Marlon GOP•2y ago

Aah ... Ok. So for me to learn how to read code, if there is a word (name) followed by {}, then that is an object because of the curly braces, while properties always have : between the key and value?

13eck•2y ago

Wait, I'm explaining it a bit wrong The key/value pairing is what's considered the property

Å Marlon GOP•2y ago

And so spaceship is only different form the nested objects because it is a variable connected object?

13eck•2y ago

So the yearBuilt key and 2018 value combined are a property on the telescope object. My apologies for the incorrect information

Å Marlon GOP•2y ago

Summarized: Objects -> {} Property -> : What really through me off was that I assumed any new object had to have the = before the {} as in spaceship ...

13eck•2y ago

The = is the assignment operator. It means "the stuff after is stored in a variable named by the stuff before"

The assignment (=) operator is used to assign a value to a variable. The assignment operation evaluates to the assigned value.

–https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Assignment

An object initializer is a comma-delimited list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}).

–https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer

Gaming

Programming

Understanding object notation - JS newbie