undefined == null code example

Example 1: null + undefined

console.log(null === null);  // true
  console.log(undefined === undefined);  // true
  console.log(null + undefined === null + undefined); // false

// null + undfined equals NaN, and NaN isn't equal to itself :(

Example 2: null undefined javascript

Undefined  used for unintentionally missing values.

Null       used for intentionally missing values.

Example 3: javascript check for null variables

var myVar=null;

if(myVar === null){
    //I am null;
}

if (typeof myVar === 'undefined'){
    //myVar is undefined
}