Answers for "differences between var, let and const in javascript"

var vs let vs const

var: 
	- hoisted (always declared at top of scope, global if none)
    - function scope
let:
    - block scope
    - not redeclarable
const: 
    - block scope
    - not reassignable
    - not redeclarable
    
Note: Although it may seem like these hold only semantic meaning, using the
appropriate keywords helps the JS engines' compiler to decide on what to optimize.

what is the difference between let and const in javascript

The difference is that with const you can only only assign a value to a variable
once, but with let it allows you to reassign after it has been assigned.