JavaScript Map

const myMap = new Map([
    ['7', 'a Number Key'],
    [1, 'a String Key'],
    [false, false]
]);

console.log(myMap);

const capital = new Map([
    ['Tokyo', 'Japan'],
    ['Canberra', 'Australia'],
    ['Kuala Lumpur', 'Malaysia'],
    ['Bangkok', 'Thailand']
]); 

console.log(capital.size);
console.log(capital.get('Kuala Lumpur'));
capital.set('Dublin', 'Ireland');
console.log(capital.size);
console.log(capital.get('Dublin'));