var a; console.table(a) //shows undefined
An assignment value is null. It can be assigned to a variable as a no-value representation.
var a= null; console.table(a); //shows null
Undefined and null are two distinct types, as shown in the preceding examples: undefined is a type (undefined), whereas null is an object.
null === undefined //false null == undefined //true null === null //true null = 'value' //ReferenceError undefined = 'value' // 'value'