Null - MDN Web Docs Glossary: Definitions of Web-related terms | MDN (2024)

FAQs

What is null in JavaScript MDN? ›

The null value represents the intentional absence of any object value. It is one of JavaScript's primitive values and is treated as falsy for boolean operations.

The value null means that no value exists. When used as a value, null is not a memory location. Only pointers hold memory locations. Without a null character, a string would not correctly terminate, which would cause problems.

In JavaScript, null and undefined represent the absence of a value. null is an assignment value that represents no value or no object. It is often used to indicate that a variable has no value or that an object does not exist.

Mozilla Developers Network(MDN)

The MDN web docs is an excellent resource for web developers. It gives an in-depth explanation of almost all concepts in JavaScript(including ES6) CSS and HTML. It a well-trusted source of knowledge. It also has a collection of articles curated to help beginners get into web development.

In computer science, a null value represents a reference that points, generally intentionally, to a nonexistent or invalid object or address.

Null is a special data type which can have only one value: NULL. A variable of data type NULL is a variable that has no value assigned to it.

null is one of the most active, open security communities. Registered as a non-profit society in 2010. One of the main objectives for null is spreading information security awareness.

Null means having no value; in other words null is zero, like if you put so little sugar in your coffee that it's practically null. Null also means invalid, or having no binding force. From the Latin nullus, meaning "not any," poor, powerless null is not actually there at all. Or if it was, it's gone now.

In source code, the null character is often represented as the escape sequence \0 in string literals (for example, "abc\0def" ) or in character constants ( '\0' ); the latter may also be written instead simply as 0 (without quotes nor slash).

Null Doesn't Trigger Default Values

If you have variables that could be indiscriminately set to either null or undefined (a situation which is very likely if you are allowing both into your application code), these default values will not always be applied as you are likely to want them to be applied.

When to use null? ›

The primitive type null indicates the intentional absence of a value. Therefore, in JavaScript, programmers often assign null to a variable to denote that the variable is declared and initialized and currently doesn't hold a value. Still, a value can be expected in the future.

Checking for Undefined or Null Using the Identity Operator (===) If you want to check if a value is specifically undefined or null without type coercion, you can use the identity operator ( === ). The identity operator checks for both value and type equality, which means it does not perform type coercion.

I think for really small tasks in HTML and CSS then w3schools is fine. But if you are looking for more substantial and trusted web development content than MDN is better.

(Mobile Directory Number) The 10-digit telephone number that is dialed to reach a CDMA or TDMA cellphone. Prior to changing carriers and porting the old number to the new carrier, the MDN and "MIN" (mobile identification number) are often the same.

MDN Web Docs, previously Mozilla Developer Network and formerly Mozilla Developer Center, is a documentation repository and learning resource for web developers. It was started by Mozilla in 2005 as a unified place for documentation about open web standards, Mozilla's own projects, and developer guides.

Conceptually, undefined indicates the absence of a value, while null indicates the absence of an object (which could also make up an excuse for typeof null === "object" ).

Comparisons convert null to a number, treating it as 0 . That's why (3) null >= 0 is true and (1) null > 0 is false. On the other hand, the equality check == for undefined and null is defined such that, without any conversions, they equal each other and don't equal anything else. That's why (2) null == 0 is false.

Both undefined and null are falsy by default. So == returns true. But when we use the strict equality operator (===) which checks both type and value, since undefined and null are of different types (from the typeof Operator section), the strict equality operator returns false.

In JavaScript null is "nothing". It is supposed to be something that doesn't exist. Unfortunately, in JavaScript, the data type of null is an object. You can consider it a bug in JavaScript that typeof null is an object.