1null is a special object because typeof null returns 'object'. 
2On the other hand,
3undefined means that the variable has not been declared,
4or has not been given a value.

1var myVar=null;
2
3if(myVar === null){
4    //I am null;
5}
6
7if (typeof myVar === 'undefined'){
8    //myVar is undefined
9}
10

1  console.log(null === null);  // true
2  console.log(undefined === undefined);  // true
3  console.log(null + undefined === null + undefined); // false
4
5// null + undfined equals NaN, and NaN isn't equal to itself :(

1/* In Javascript,
2* null: a value explicitly set by the programmer for the intentional lack of value.
3* undefined: a value implictily or explicitly set for the intentional lack of value.
4*/
5
6console.log(null == undefined) // true
7console.log(null === undefined) // false
8
9let a = null
10console.log(a) // null
11
12let c;
13let d = undefined;
14console.log(c, d) // undefined undefined
15
16console.log(typeof null) // Object
17console.log(typeof undefined) // undefined

1Undefined  used for unintentionally missing values.
2
3Null       used for intentionally missing values. 

1//loosely equal (compare values between two variables)
2null == undefined // true  ( null => 0 , undefined => NAN)
3
4//strictly not equal (compare both type and value) 
5null === undefined // false  (typeof null => object , typeof undefined => undefined)
6null !== undefined // true   (typeof null => object , typeof undefined => undefined) 
7