new Map()           // creates the map
map.set(key, value) // stores the value against the key
map.get(key)        // returns the value associated with the key
map.has(key)        // true if the key exists, otherwise false
map.delete(key)     // removes the value by the key
map.clear()         // clears the map
map.size            // returns the current element count   

const map = new Map();

map.set('123', 'string keys are cool');
map.set(123, 'number keys are cooler');
map.set(true, 'too true!');

// A regular Object would convert keys to strings,
// so these two would not be different:

console.log(map.get('123'));    // 'string keys are cool'
console.log(map.get(123));      // 'number keys are cooler'

console.log(map.size);          // 3

const ariela = {name: 'Ariela'};
const takayoshi = {name: 'Takayoshi'};

const ages = new Map();

// Note that map methods return themselves, so you can chain
ages.set(ariela, 53) 
    .set(takayoshi, 30);

console.log(ages.get(ariela)); // 53

const map = new Map([
  ['name', 'Takayoshi'],
  ['age', 30]
]);

const map = new Map(Object.entries({
  name: 'Takayoshi',
  age: 30
}));

const menu = new Map([
  ['avo poached eggs', 13],
  ['grilled grapefruit', 6],
  ['coconut chia pot', 7]
]);

for (let menuItem of menu.keys()) {
  console.log(menuItem);    // avo poached eggs, grilled...
}

for (let amount of menu.values()) {
  console.log(amount);     // 13, 6, 7
}

for (let entry of menu) { // Same as of menu.entries()
  console.log(entry);     // avo poached eggs,13...
}

menu.forEach((value, key, map) => {
  console.log(`${key}: ${value}`); // avo poached eggs: 13 etc
});

new Set(iterable)       // creates the set
set.add(value)          // adds a value
set.delete(value)       // removes value, returns true if value existed
set.has(value)          // returns true if the value exists in the set
set.clear()             // removes everything from the set
set.size                // returns the current element count

const visits = new Set();

const ariela = {name: 'Ariela'};
const takayoshi = {name: 'Takayoshi'};
const lana = {name: 'Lana'};

// Visits, some users come multiple times
visits.add(ariela);
visits.add(takayoshi);
visits.add(lana);
visits.add(ariela);
visits.add(lana);

console.log(visits.size); // 3 - only unique values

for (let user of visits) {
  console.log(user.name); // In order: Ariela, Takayoshi, Lana
}

const morningTea = new Set(['croissant', 'macaron', 'financier']);

for (let value of morningTea) {
    console.log(value);
}

// Note the weirdness here
morningTea.forEach((value, valueAgain, morningTea) => {
    console.log(value);
});

// Both print croissant, macaron, financier

let ariela = {name: 'Ariela'};

// The object can be accessed, ariela is the reference to it

// Let's overwrite the reference..
ariela = null;

// The object will be removed from memory

let lana = {name: 'Lana'};

const weakAgeMap = new WeakMap();

// Keys must be Objects
weakAgeMap.set(lana, 8);

lana = null; // Overwrite the reference

// There are no references except WeakMap, so the Lana object is
// removed both from the memory and from weakAgeMap automatically

weakMap.get(key)
weakMap.set(key, value)
weakMap.delete(key, value)
weakMap.has(key)

const messages = [
    {text: 'How do you like your eggs?', from: 'Takayoshi'},
    {text: 'Scrambled', from: 'Ariela'},
    {text: 'Let\'s do brunch!', from: 'Lana'}
];

// Fill it with array elements (3 items)
const unreadSet = new WeakSet(messages);

// We can use unreadSet to see whether a message is unread
console.log(unreadSet.has(messages[1])); // true

// Remove it from the set after reading
unreadSet.delete(messages[1]); // true

// If we remove an item from our message list, the set is
// cleaned up automatically
messages.shift();

// No need to clean unreadSet, it now has 2 items
// unfortunately, there's no method to get the exact count
// of items, so can't show it