JAVASCRIPT

var vs let js

let: //only available inside the scope it's declared, like in "for" loop, 
var: //accessed outside the loop "for"

difference between let and var in javascript

//let
1. It's used in block-scoped.
2. It does not allow to redeclare variables.	
3. Hoisting does not occur in let.
// var 
1. It's used in function scoped.
2. It allows to redeclare variables.
3. Hoisting occurs in var.

js var vs let

let = 10 // accessable only in defined scope
var = 10 // accessable in the function it is declared in (global variable in a function)
  

what to use let vs var js

/* DIFFERENCE BETWEEN LET AND VAR */

//LET EXAMPLE
{
  let a = 123;
};

console.log(a); // undefined

//VAR EXAMPLE
{
  var a = 123;
};

console.log(a); // 123

var vs let javascript

var makes a grobal variable
let makes a local variable