map(), forEach(), and filter() are the array method in es6 in Js. which is work on - each element of array.

• map()- transforms each element of array and returns a new array. Usege - When we try or need to modified array.
• forEach() – loops over elements but does not return anything in the array. Usege - When you just need to use loop over elements like as for-loop.
• filter() – also returns a new array, only the filtered elements that Pass by a specific Condition. Usage - When we need to filtered any element of the array.

In javacript arrow functions are a shorter and more concise campare to functions.It is a a element of ES6 but normal function is not.

• arrow functions (=>) For one-line expression no need for function return. But for more line expresion function return is is needed.
• Regular Function( keyword - function() ) Declared variables are block-scoped. Which means - only accessible inside the block {} where it is declared. let variables can be changeable same as var.

A Promise is an object that represents the eventual completion (or failure) of an asynchronous operation. It allows you to handle asynchronous tasks. There are mainly 3 stage of promis is:-

• Pending
• Resolved
• Rejected

A closure is a function which is create by under another function and parent function varible are remembers.

In JavaScript Es6 closures are a powerful feature which is help retain state, create private variables, and manage async code efficiently.