Javascript - Explanation About Map, WeakMap, Set, WeakSet & It's Operations

#javascript #set #map #javascript_tutorial #operations

What is a Map?
Map is a collection of elements where each element is stored as a Key, value pair. Map object can hold both objects and primitive values as either key or value. When we iterate over the map object it returns the key, value pair in the same order as inserted.

Map used for?
map() creates a new array from calling a function for every array element. map() calls a function once for each element in an array.

Advantages of Map:
In a Map, there is more flexibility with key values, as a key can be any value such as functions, objects, and primitives. In an Object, a key can only be a string or symbol. Depending on how you are storing your data, Map's flexibility with more data types could be useful.

Difference between Map and Filter:
Map: returns an array of pieces of information from the original array. In the callback function, return the data you wish to be part of the new array. Filter: returns a subset of the original array based on custom criteria.

Why Map is used instead of an Array?
While an Array , as brought up in the question, is also iterable, a Map offers a better use-case for key-value mappings than an Object would. Being iterable has a number of benefits, just-in-time execution and guaranteed order being two examples.

Difference between forEach() and map():
The forEach() method does not returns a new array based on the given array. The map() method returns an entirely new array. The forEach() method returns “undefined“. The map() method returns the newly created array according to the provided callback function.

What is a WeakMap in Javascript?
A WeakMap is a collection of key/value pairs whose keys must be objects, with values of any arbitrary JavaScript type, and which does not create strong references to its keys. That is, an object's presence as a key in a WeakMap does not prevent the object from being garbage collected.

Difference between Map and WeakMap?
1) A WeakMap accepts only objects as keys whereas a Map,in addition to objects, accepts primitive datatype such as strings, numbers etc.
2) WeakMap objects doesn't avert garbage collection if there are no references to the object which is acting like a key.

What is a Set in Javascript?
A JavaScript Set is a collection of unique values. Each value can only occur once in a Set. A Set can hold any value of any data type.

Difference between Set and Array in Javascript:
Array is faster than set in terms of initialization. Set is slower than an array in terms of initialization because it uses a hash process. The array allows storing duplicate elements in it. Set doesn't allow you to store duplicate elements in it.

Why we use Sets in Javascript?
The Set object lets you store unique values of any type, whether primitive values or object references.

Advantage of Set:
Set can be used to store unique values in order to avoid duplications of elements present in the set. Elements in a set are stored in a sorted fashion which makes it efficient. Set are dynamic, so there is no error of overflowing of the set.

Different types of Sets:
Empty Set or Null set: It has no element present in it.
Finite Set: It has a limited number of elements.
Infinite Set: It has an infinite number of elements.
Equal Set: Two sets which have the same members.

The empty set, finite set, equivalent set, subset, universal set, superset, and infinite set are some types of set.

What is WeakSet in Javascript?
WeakSet s are collections of objects only. They cannot contain arbitrary values of any type, as Set s can. The WeakSet is weak, meaning references to objects in a WeakSet are held weakly. If no other references to an object stored in the WeakSet exist, those objects can be garbage collected.

What is WeakSet and WeakMap in Javascript?
WeakMap is Map -like collection that allows only objects as keys and removes them together with associated value once they become inaccessible by other means. WeakSet is Set -like collection that stores only objects and removes them once they become inaccessible by other means.

Set Operations in Javascript:
A JavaScript Set is a collection of unique values. Each value can only occur once in a Set.

You can create a JavaScript Set by:
Passing an Array to new Set()
Create a new Set and use add() to add values.
Create a new Set and use add() to add variables.