undefined is a global variable which has the value undefined — a datatype by itself which can have only one value. But what is the value null?

MDN says:

The value null is a literal.

What does that mean?

I know literal as "something you write fixed into your code". Like x = 3 + 4.

Here 3 and 4 would be integer-literals. But I don't get that together with what the MDN documentation says.

undefined is a global variable which has the value undefined — a datatype by itself which can have only one value. But what is the value null?

MDN says:

The value null is a literal.

What does that mean?

I know literal as "something you write fixed into your code". Like x = 3 + 4.

Here 3 and 4 would be integer-literals. But I don't get that together with what the MDN documentation says.

• javascript

• 2 Literals – hindmost Commented Mar 23, 2016 at 8:24
• 1 @T.J.Crowder you're dead right. I was reading about it this morning on the way to work, and got it all mixed up :-(... ah well, it will stick now – Paul Fitzgerald Commented Mar 23, 2016 at 8:33
• Duplicate: Javascript null object type – Yogi Commented Mar 23, 2016 at 8:35

4 Answers 4

Literals are just a way to write values in our code. null, the thing you actually type, is a literal that defines the value null, just like 1 is a literal that defines the value 1. The null value is just that: A value (the only value in the Null type), like 1 is a value (one of many values in the Number type).

Remember that MDN is a munity-edited resource. It's usually pretty good, but it es down to who wrote and/or subsequently edited the page. Sometimes the terminology is a bit off. Let's look at the opening sentence of that page as it was when you posted your question:

The value null is a JavaScript literal representing null or an "empty" value, i.e. no object value is present.

Yeah, that looks like an editing error. It should read something like:

The value null represents the intentional absence of any object value.

I'll probably edit it later. I've edited it and the subsequent line that's trying to highlight that null is a literal, not an identifier for a property on the global object like undefined can be.

I am no expert but I think you already have the answer: you said 3 and 4 are "integer-literal". Quoting wikipedia:

In puter science, a literal is a notation for representing a fixed value in source code.

So 3 and 4 are both literals, as well as 34 or "hello". null is a literal in the same way, but instead of representing a number or a string, is has a meaning of nothingness.

EDIT: As I said, I am no expert and it seems I am not quite right about literals. T.J. Crowder explains it much better than me, see his answer

Null is one of the primitives in JS.

This primitive type is used as a literal in some cases which need to represent an absence of a value in a variable or reference.

However said, the literal value of null has a special meaning.

Point worth noting is that:

typeof null        // object (bug in ECMAScript, should be null)
typeof undefined   // undefined
null === undefined // false
null  == undefined // true

null is not an object , has no methods , and is absent of any value

See Null

In puter science, a null value represents a reference that points, generally intentionally, to a nonexistent or invalid object or address. The meaning of a null reference varies among language implementations.

In JavaScript, null is one of the primitive values.

Primitive

A primitive (primitive value, primitive data type) is data that is not an object and has no methods

4.3.12 null value

primitive value that represents the intentional absence of any object value

4.3.13 Null type

type whose sole value is the null value