javascript - delete operator with var and non var variables

Question

I tried delete a variable in javascript using delete operator, but found some issue. Can you guys please explain the below code, and why it is happening

>> var a = 5;

>> delete a
false

>>a
5

>> b=5;

>>delete b
true

>>b
ReferenceError b is not defined

why var a = 5 and b = 5 are different?

Answer 1

Without using var, assignment with the = operator is always assigning a property, in your second case the object is implicitly the global object (window in your browser).

The delete operator is only for deleting properties on objects, not normal variables.