JAVASCRIPT

1> Difference between var and let in javascript

--- var is scoped to the nearest function block while let is enclosed to the nearest enclosing block.

     

 
--- Both are global if outside any block.

> const statement values can be assigned once and they cannot be reassigned. 
example:

function nodeSimplified(){

  const MY_VARIABLE =10;

  console.log(MY_VARIABLE);  //output 10

  MY_VARIABLE =20;           //throws type error

  console.log(MY_VARIABLE); 

}

2> Difference between == and ===

Ans: == just compares value while === compares value and type both.

3> what is the difference between "undefined" and "null" keywords?

--- undefined means variable has been declared but has not been assigned a value. 

While null can be assigned to variable representing no value.

null === undefined // false
null == undefined // true

if we do typeof undefined it gives undefined while if we do typeof null it gives object.

Q.what is use of Arrow function?
Ans.