What does it mean to say that "null is a literal" in JavaScript?

Question

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.

Answer 1

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 community-edited resource. It's usually pretty good, but it comes 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.

Answer 2

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

In computer 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

Answer 3

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