ES6 Maps

Maps are a new object structure introduced in ES6. A map is an object that holds key-value pairs.

// MAPS = key-value pairs - can use ANY type as a key or value

const map1 = new Map();

// Set Keys
const key1 = 'some string',
      key2 = {},
      key3 = function(){};

// Set map values by key
map1.set(key1, 'Value of key1');
map1.set(key2, 'Value of key2');
map1.set(key3, 'Value of key3');

// Get values by key
//console.log(map1.get(key1), map1.get(key2), map1.get(key3));

// Count values
//console.log(map1.size);

// Iterating through MAPS

// Loop using for...of to get keys and values
for(let [key, value] of map1){
    console.log(`${key} = ${value}`);
}

// Iterate keys only
for(let key of map1.keys()){
    console.log(key);
}


// Iterate values only
for(let value of map1.values()){
    console.log(value);
}


// Loop with forEach
map1.forEach(function(value, key){
    console.log(`${key} = ${value}`);
});

// CONVERT SETS TO AN ARRAYS
// Create an array of the key value pairs
const keyValArr = Array.from(map1);
console.log(keyValArr);

// Create an array of values
const valArr = Array.from(map1.values());
console.log(valArr);

// Create an array of keys
const keyArr = Array.from(map1.keys());
console.log(keyArr);