Hackforge Academy

Explanation

In JavaScript, a Map is a built-in object that stores key–value pairs. Unlike normal objects, Map allows keys of any type (objects, functions, primitives) a preserves insertion order.

Code:

const map = new Map();
map.set('name', 'Praveen');
map.set('age', 25);
map.set(1, 'Number Key');
console.log(map.get('name'));

Explanation

set() method adds or updates a key-value pair in a Map.
get() method retrieves the value associated with a specified key.

Code:

const map = new Map();
map.set('language', 'JavaScript');
map.set('version', 'ES6');

const map = new Map();
map.set('framework', 'React');
console.log(map.get('framework'));

Explanation

has() method checks whether a Map contains a specific key.
delete() method removes a specific key-value pair from the Map.

Code:

const map = new Map();
map.set('database', 'MongoDB');
console.log(map.has('database'));
console.log(map.has('sql'));

map.set('backend', 'Node.js');
map.delete('backend');
console.log(map.has('backend'));

Explanation

Clear() method removes all key-value pairs
size property returns the number of key-value pairs in the Map.

Code:

const map = new Map();
map.set('a', 1);
map.set('b', 2);
map.clear();
console.log(map.size);

map.set('x', 10);
map.set('y', 20);
console.log(map.size);

Explanation

keys() returns an iterator containing all keys in the Map.
values() returns an iterator containing all values in the Map.

Code:

const map = new Map([
['name', 'hackforge'], 
['course', 'fullstack']
]);

for (let key of map.keys()) {
  console.log(key);
}
for (let value of map.values()) {
  console.log(value);
}

Explanation

entries() method an iterator containing key-value pairs from the Map.
forEach() executes a callback function for each key-value pair in the Map.

Code:

const map = new Map([
['name', 'hackforge'], 
['course', 'fullstack']
]);

for (let [key, value] of map.entries()) {
  console.log(key, value);
}
map.forEach((value, key) => {
  console.log(key + ': ' + value);
});