Tricky Concepts

Scope

Scope simply allows to know where we have access to our variables. In simple words, Scope is the accessibility of variables, function and objects in some particular part of code during runtime.

Types of Scope:

1. Global Scope
2. Local Scope
3. Block Scope (only with let and const)

• Global Scope:

  Variables declared Globally (outside any function) have Global Scope. Global variables can be accessed from anywhere in a JavaScript program. Variables declared with var, let, and const are quite similar when declared outside a block. They all have Global Scope.

• Local / Function Scope:

  Variables which are declared within a function, as well as the function parameters have local scope. That means they are only visible within that function.

• Block Scope:

  let and const keywords provide Block Scope in JavaScript. Variables declared inside a {} block cannot be accessed from outside the block.

Hoisting

Hoisting is a JavaScript mechanism, where variables and function declaration are moved to the top of their scope before code execution.

Closure

A Closure defined as, the inner function has access to the outer function variable. In JavaScript, every time a closure is created with the creation of a function.