Health App, User dashboard

• 308.272 total steps
• 1.826 total floors
• 211.70 total miles
• 5.755 avg. daily calorie burn
• 2312 total active minutes
• 7 of 5 days exercising this week
• 2 hrs 13 mins of restful sleep

If we used an array, we definitely could, It just would be confusing and we'd have to come up with some arbitrary rules.

• Objects are collections of properties
• Properties are a key-value pair
• Rather than accessing data using an index, we use custom keys

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object

In objects we don't use a number to access our data out like we do with an array where we say, give me the index of one item instead, Example: give me city, please or give me zip or age and you get the corresponding value.

You have a key and it's kind of a one way relationship, you put the key in and you figure out the corresponding value.

username: '@ElfGodd',
age: 36,
city: 'Barranquilla',
zip: 101001,
text: 'great post!',
upvotes: '7',
isAdmin: true

const fitAppData = {
  totalSteps: 308727,
  totalMiles: 211.7,
  avgCalorieBurn: 5755,
  workoutsThisWeek: '5 of 7',
  avgGoodSleep,: '2:13'
};

ALL TYPES WELCOME!

let comment = {
  username: 'sillyGoose420',
  downVotes: 19,
  upVotes: 214,
  netScore: 195,
  commentText: 'Tastes like chicken lol',
  tags: ['#hilarious', '#funny', '#silly'],
  isGilded: false
};

All keys are converted to strings, Except for Symbols
key: value === string: data

// This is converted
const numbers = {
  100: 'one hundred',
  16: 'sixteen'
}
// to this
const numbers = {
  '100': 'one hundred',
  '16': 'sixteen'
}

Why would you use square brackets aside from if you tried to store numbers as a key, Well sometimes you have property names that may not be valid JavaScript identifiers. Now, an identifier in JS is like the name of a variable.

// invalid name variable
// invalid indentifier or unexpected token
// i cannot have a variable name, start with a number
let my cat = 'Elf Cat'
let 76games = 'NBA team'

// But that doesn't mean we can't do that as a key in an object
object = {
  '76 trombones': 'great song!'
}
console.log(numbers2['76 trombones']); // 'great song!'

Another reason sometimes you want to use a dynamic value like a variable to access data from an object.

const palette = {
  red: '#eb4d4b',
  yellow: '#f9ca24',
  blue: '#30336b'
}

palette.red // '#eb4d4b'
palette['blue'] // '#30336b'

let color = 'yellow';
palette.color // undefined property doesn't exist 'color'
palette[color] // '#f9ca24'

My general rule of thumb is to try and use the dot notation whenever possible. It is shorter and nicer to look, but when it's not possible, whether it's because you have a key name that is not valid as a identifier like let 76games = 'NBA team'

It's similar to viewing a property or accessing the data. We have the dot notation or the square brackets. The only difference is we use an equal sign to assign a value either to update that value or to give it an initial value.

// Updating properties:
fitAppData.workoutsThisWeek = '6 of 7';
fitAppData.totalMiles += 7.5;

// Adding a new property
fitAppData.heartStillBeating = true;

const shoppingCart = [
  {
    product: 'Jenga Classic',
    price: 6.88,
    quantity: 1
  },
  {
    product: 'Echo Dot',
    price: 29.99,
    quantity: 3
  },
  {
    product: 'Fire Stick',
    price: 39.99,
    quantity: 2
  }
]

const student = {
  firstName: 'Alberto',
  lastName: 'Guzman',
  strengths: ['Programmer', 'Futbol'],
  exams: {
    midterm: 92,
    final: 88
  }
}

const game = {
  player1: { username: 'Blue', playingAs: 'X' }
  player2: { username: 'Muffins', playingAs: '0' }
  board : [
    ['0', null, 'X'],
    ['X', '0', 'X'],
    [null, '0', 'X']
]};

Arrays and Objects behave the same way when we checking for equality we are comparing Reference Types Addresses.

When we compare with == or ====, we're comparing these memory slot addresses, variables might look the same, but it has it's own completely unique place in memory.

let nums = [1, 2, 3];
let mystery = [1, 2, 3];

console.log(nums == mystery); // false
console.log(nums === mystery); // false

nums -> 12873612783
mystery -> 9912873621

let moreNums = nums;
console.log(nums === moreNums); // true

This means if you're trying to compare arrays, if you're trying to see if an array is equal to another array, it's not as straightforward as you might hope it would be, because a lot of times you're not trying to check if an array is the exact same array, Instead you often want to check if they look the same, if they contain the same information.

So the next thing that it's a little trickier is trying to check if an array contains or looks like another array that isn't empty.

So if i wanted to know if one array contained exactly the numbers one, two and three in that order, unfortunately there's not an easy option for us right now until we talk about loops. We don't really have a way of checking for array equality of values, what we will need to do is manually compare every element in an array to another array.

The exact same thing holds true for objects.