Only use null if you explicitly want to denote the value of a variable as having “no value”. As @com2gz states: null is used to define something programmatically empty. undefined is meant to say that the reference is not existing. A null value has a defined reference to “nothing”.
When should you use null?
Allow null only if it makes sense for an object reference to have ‘no value associated with it’. Don’t use null to signal error conditions. The concept of null exists only for reference types. It doesn’t exist for value types.
Why do we use null?
Null or NULL is a special marker used in Structured Query Language to indicate that a data value does not exist in the database. … SQL null is a state, not a value. This usage is quite different from most programming languages, where null value of a reference means it is not pointing to any object.
isNull() function: It is used to find whether the value of the object is null. If object has null value then the output will be true otherwise false. We can even perform addition, subtraction etc operations in this function.
Pass the object to the Object. keys method to get an array of all the keys of the object. Check if the length of keys is equal to 0 , if it is, then the object is empty. …