JavaScript Core Concepts

What is Scope?

Scope determines the accessibility of variables, objects, and functions from different parts of the code.

Map() vs forEach()

Some of the difference between map() and forEach() methods are listed below :−

The map() method returns a new array, whereas the forEach() method does not return a new array.

The map() method is used to transform the elements of an array, whereas the forEach() method is used to loop through the elements of an array.

The map() method can be used with other array methods, such as the filter() method, whereas the forEach() method cannot be used with other array methods.

Final Thoughts:

As always, the choice between map() and forEach() will depend on your use case. If you plan to change, alternate, or use the data, you should pick map(), because it returns a new array with the transformed data.

But, if you won't need the returned array, don't use map() - instead use forEach() or even a for loop.

Syntax:
 forEach((currentElement, indexOfElement, array) => { ... } )

 map((currentElement, indexOfElement, array) => { ... } )

Parameters:
  - currentElement: This is the current element that is being processed in the callback.
  - indexOfElement: The index of that current element inside the array.
  - array: The array on which the whole operation is being performed.
map() forEach()

- The map() method returns an entirely new array. - The forEach() method does not returns a new array based on the given array.

- The map() method returns the newly created array according to the provided callback function. - The forEach() method returns “undefined“.

- With the map() method, we can chain other methods like, reduce(),sort() etc. - The forEach() method doesn’t return anything hence the method chaining technique cannot be applied here.

- It does not change the original array. - It is not executed for empty elements.

Optional Chaning (?.)

The optional chaining ?. is a safe way to access nested object properties, even if an intermediate property doesn’t exist.

The optional chaining (?.) operator accesses an object's property or calls a function.

If the object accessed or function called using this operator is undefined or null, the expression short circuits and evaluates to undefined instead of throwing an error.

Reference: https://javascript.info/optional-chaining

Convert Number to String, String to Number & String to Array, Array to String & Array to Object, Object to Array ?

Number to String: toString()
String to Number: parseInt()

Array to String: toString() or join()
String to Array: split()

Array to Object: reduce() or using destructuring Eg: {...arr}
Object to Array: Object.keys() & map() Or Object.entries()

Array to Set: new set(arr)
Set to Array: Array.form(set) Or [...set]