What are the differences between variables created using let, var or const?

Scope

var

• If a variable is created inside a function, it is scoped to the function
• If a variable is created outside of any function, it is scoped to the global object

let & const

• let and const are block scoped
• let and const are only accessible within the nearest set of curly braces (function, if-else block, or for-loop)

Hoisting

• Javascirpt hoisting: move all declarations to the top of the current scope (current script/current function), so a variable can be used before it has been declared.
• var allows variables to be hoisted
• let and const will NOT allow hoisted

Redeclaring

• redeclaring a variable with var will NOT throw an error
• redeclaring a variable with let or const will throw an error

Reasigning

• let allows assigning the variable's value
• const does NOT allow assigning the variable's value

ref:

• https://www.w3schools.com/js/js_hoisting.asp
• https://github.com/yangshun/front-end-interview-handbook/blob/master/questions/javascript-questions.md#what-are-the-differences-between-variables-created-using-let-var-or-const