2 Answers. The value null represents the intentional absence of any object value. You also get undefined when you call a non-existent property or method of an object.
null and undefined both return false . That’s why your code is actually checking if false is equal to false . However their types are not equal. Because of that, the next statement will return false, as the === comparison operator checks both the types and their value.
Is null == undefined?
null is an assigned value. It means nothing. undefined means a variable has been declared but not defined yet.
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.
What is better null or undefined?
Use null for set a variable you know it is an Object. Use undefined for set a variable whose type is mixed.
Should I return null or undefined?
Undefined typically refers to something which has not yet been assigned a value (yet). Null refers to something which definitively has no value. In that case, I would recommend returning a null. Note that a function with no specified return value implicitly returns undefined.
Summary. null is an assigned value. It means nothing. undefined typically means a variable has been declared but not defined yet.
isNaN() method determines whether a value is NaN (Not-A-Number). This method returns true if the value is of the type Number, and equates to NaN. Otherwise it returns false. … isNaN() does not convert the values to a Number, and will not return true for any value that is not of the type Number.
Is null false in Java?
In Java, null is a keyword much like the other keywords public, static or final. It is just a value that shows that the object is referring to nothing. … When you declare a boolean variable, it gets its default value as false. Similarly, any reference variable in Java has null as a default value.