Javascript :: Objects #js

Objects1.js

// way to define object: with {}:

pusheen = {
    name: 'Pusheen',
    age: 7,
    'color': 'gray'',
    'cat sound': 'meow'
};
// left side is 'keys' and must use quotes only if the key is two words with a space in between

// can refer to them using brackets
console.log(pusheen['age']) <--- must use quotes because using bracket notation
// if you use quotes in key during object def then must use it when called:
console.log(pusheen['color'])
>gray

// or dot notation but NOT with keys that are in quotes!:
console.log(pusheen.age)
console.log(pusheen.'color')  <--- unacceptable; must use bracket notation for this
>7

// can use concatenation with bracket notation but not with dot notation 
console.log(pusheen['sound' + " " + 'sound']);

// can add to object easily:
pusheen['owner'] = "Meg";
// or
pusheen.owner = "Meg";

// remove a key entry:
delete pusheen.owner;
// or
delete pusheen['owner'] <--- must use quotes because using bracket notation

// other examples:
pusheen.age++



// for loops
for (let key in pusheen) {
    console.log(key); // outputs all the keys
    console.log(pusheen[key]); // outputs all the values
    //but cannot use console.log(pusheen.key) because JS recognizes that as a string
    console.log("Her " + key + " is " + pusheen[key]);
}

>Her name is Pusheen
>Her age is 7
>Her color is gray
>Her cat sound is meow


console.log(Object.keys(pusheen));
>[ 'name', 'age', 'color', 'cat sound' ]

let keys = Object.keys(pusheen);
for (let i=0; i < keys.length; i++) {
    console.log(pusheen[keys[i]]);
}

// object keys can also hold arrays:
pusheen.color = ['gray', 'tabby']
console.log(pusheen.color[1]);
>tabby

// object keys can also hold other objects (NESTED OBJECTS):
pusheen.siblings = {
    sister: 'Mary',
    brother: 'Joe'
};
console.log(pusheen.siblings.sister);
>Mary