Var Let Const

#Var

1. Variable declared with var goes to global scope.
2. We can redeclare variable with same name in same scope.
3. We can update the value of variable.
4. We can declare variable without initialization.
5. Variable declared with var , can be hoisted.
6. Variable declared inside block , will go to global scope.
7. Variable declared inside function , will not go to global scope. It will be accessible inside function only.

#Let

1. Variable declared with let is block scoped.
2. We cannot redeclare variable with same name in same scope.
3. We can update the value of variable.
4. We can declare variable using let without initialization. But js engine will keep that memory block uninitialized (empty) untill js engine reads declaration statement in execution phase.
5. Because let variable is uninitialized (empty) in variable phase , it belongs to Temporal Dead Zone.
6. The variable declared using let does not belongs to global scope , we cannot access them with the help of window variable.
7. The variable declared using let is hoisted and belongs to temporal deadzone. Therefore it cannot be used before initialization (because at that moment it is uninitialized - TDZ) .
8. Variable declared inside function will be accessible inside function only.

#Const

1. Variable declared with const is block scope.
2. We cannot redeclare variable with same name in same scope.
3. The value of variable can not be modified.
4. We can not declare const without initialization.
5. The variable declared using const is hoisted and belongs to temporal deadzone. Therefore it cannot be used before initialization (because at that moment it is uninitialized - TDZ) .
6. The variable declared using const inside block ,does not belongs to global scope we cannot use them with the help of window.
7. Variable declared inside function will be accessible inside function only.

#Practice Questions

1console.log("start");
2let a = 10;
3var b = 20;
4const c = 30;
5{
6  let a = 100;
7  var b = 200;
8  const c = 300;
9  console.log(a);
10  console.log(b);
11  console.log(c);
12}
13console.log(a);
14console.log(b);
15console.log(c);
16console.log("end");

1console.log("start");
2let a = 10;
3console.log(b);
4{
5  var b = 200;
6}
7console.log(a);
8console.log(b);
9console.log("end");

1console.log("start");
2let a = 10;
3{
4  console.log(a);
5  let a = 10;
6}
7console.log(a);
8console.log(b);
9console.log("end");

1console.log("start");
2var b = 20;
3const c = 30;
4{
5  let a = 100;
6  console.log(a);
7  console.log(b);
8  console.log(c);
9}
10console.log(a);
11console.log(b);
12console.log("end");

1console.log("start");
2let a = 10;
3var b = 20;
4const c = 30;
5{
6  let a = 10;
7  console.log(a);
8  const c = 300;
9  console.log(b);
10  b = 200;
11  c = 30;
12  console.log(b);
13}
14console.log(a);
15console.log(b);
16console.log("end");