Day 26: Maps

Welcome back to the day 26th of DailyJS, I know I was a little inconsistent in putting up the content from past few days, I will try to be more consistent from now :D

Today’s topic is map, which is, again, a very simple topic.

If you come from some other language you must have heard about some data structures that are capable of holding key value pairs. For example, python has dictionary.

Similarly, Map is a collection of elements where each element is stored as a Key, value pair.

Syntax

The syntax is very simple, we can provide an iterable object in the constructor. We can even use the get and set methods to retrieve and set the key values.

new Map([itr])

var myMap = new Map([['a', 1], ['b', 2] ,['c', 3]]);

Some important methods -

1. Map.prototype.set () - myMap.set (key, val)
2. Map.prototype.get () - myMap.get (key)
3. Map.prototype.has () - myMap.has (key)
4. Map.prototype.delete () - myMap.delete (key)
5. Map.prototype.clear () - myMap.clear ()
6. Map.prototype.keys () - myMap.keys ()
7. Map.prototype.values () - myMap.values ()

[Example] (./1.js)

/**
 * Map in JS
 */

var myMap = new Map([['a', 1], ['b', 2] ,['c', 3]]);
console.log (myMap);
console.log ("'a' -> ", myMap.get ('a'));

// Delete all key value pairs
myMap.clear ();
console.log (myMap);

// Adding new pairs
myMap.set ('name', 'Madhav');
myMap.set ('age', 21);
myMap.set ('profession', 'Student');
myMap.set ('remarks', 'Good Boi');
console.log (myMap);

// Get the value from key
const name = myMap.get ('name');
console.log (name);

// Check a key
const hasAge = myMap.has ('age');
console.log ('myMap has age: ', hasAge);

// Delete a pair
myMap.delete ('remarks');
console.log (myMap);

That’s it for today, see you tomorrow!