Answer: Use the typeof operator If you want to check whether a variable has been initialized or defined (i.e. test whether a variable has been declared and assigned a value) you can use the typeof operator.
What is a null check?
A null indicates that a variable doesn’t point to any object and holds no value. You can use a basic ‘if’ statement to check a null in a piece of code. Null is commonly used to denote or verify the non-existence of something.
The typeof operator returns the type of the variable on which it is called as a string. This can be used to check if an object exists or not, as a non-existing object will always return “undefined”. …
How do you check if a Dataframe is null?
In order to check null values in Pandas Dataframe, we use notnull() function this function return dataframe of Boolean values which are False for NaN values.
Is null and object?
a null is an object. Its type is object . null is a special value meaning “no value. undefined is not an object, its type is undefined.