May 14, 2018 · undefined: It means that the object doesn't have any value, therefore undefined. This occurs when you create a variable and don't assign a value to it. null: It means that the object is empty and isn't pointing to any memory address.

Feb 22, 2011 · The difference between null and undefined is: JavaScript will never set anything to null, that's usually what we do. While we can set variables to undefined, we prefer null because it's not something that is ever done for us.

Apr 19, 2013 · According to the Mozilla docs: The undefined value converts to NaN when used in numeric context. So why do both of the following equate to true?: NaN != undefined NaN !== undefined I could understand Nan !== undefined as the variable type would be different...

Mar 28, 2018 · When you declare a variable but don’t declare its value, JavaScript assigns “undefined” value to it. If you try any arithmetic operations with undefined, you are going to get NaN (you can just trust me with this one or check it out on your own 🙃).

Jun 4, 2023 · Null represents the intentional absence of an object value, undefined signifies the absence of a value due to variables or functions being uninitialized, and NaN represents an invalid number....

Oct 15, 2024 · In JavaScript terms, “undefined” means something exists but hasn’t been assigned any specific value yet. It’s like when I declare a variable but don’t assign a value: I know “myVar” is there, but...

NaN and undefined are both special values in JavaScript, but they represent entirely different concepts. NaN is used to indicate an unrepresentable mathematical result, while undefined is used to signify that a variable has been declared but not yet assigned a value.

Apr 14, 2025 · Understand the key differences between null, undefined, and NaN in JavaScript with clear examples, use cases, and best practices for each.

Jan 24, 2023 · NaN means Not a number, and it denotes the value of an object is not a number. If you look at typeof NaN it will return 'number' since NaN is a numeric data type that is undefined as a real number.

NaN is a value returned by a function expecting to return a number but instead returns a value, of type number, that is not a number. Read that again. Like null, NaN is defined. It is also a built-in error message informing us of a specific problem. Each NaN is unique. Let’s compare null, undefined, and NaN.