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Question 1

What is the difference between var and let and const

Answer 1

let has a block scope.
const has a block scope.var has a function scope, not a block scope.

Question 2

what does .map() do?

Answer 2

The .map() method allows you to run a function on each item in the array, returning a new array as the result.

In React, map() can be used to generate lists.