jQuery if undefined

Answer: Use the strict equality operator (===) You can use the typeof operator in combination with the strict equality operator (===) to check or detect if a JavaScript object property is undefined.

Every JavaScript object has a special method object. hasOwnProperty(‘myProp’) that returns a boolean indicating whether object has a property myProp . hero. hasOwnProperty(‘name’) returns true because the property name exists in the object hero .

To check if an object is empty in JavaScript:

Use the strict inequality (! ==) operator to check if a variable is not null – myVar !== null . The strict inequality operator will return true if the variable is not equal to null and false otherwise.