null
In JavaScript, null is a primitive type whose only value, null, represents the intentional absence of an object value. It’s one of JavaScript’s primitive types, even though the typeof operator reports it as 'object':
> null
null
> typeof null
'object'
> null === null
true
Like every primitive, null is immutable and compares by value, so === and Object.is() both treat any two null values as the same.
null Literal and typeof
The null value is written with the null literal, which is also a reserved word, so it can’t name a variable or a function. Code usually assigns null on purpose, for example to clear a reference or to signal that a lookup found nothing:
> let selected = { id: 7 };
undefined
> selected = null;
null
> "abc".match(/x/)
null
The 'object' result of typeof null is a historical quirk from the first JavaScript engine, and the specification keeps it for compatibility. A reliable null check compares with === instead:
> const value = null;
undefined
> typeof value === "object"
true
> value === null
true
null vs. undefined
Both values mean “nothing here”, but undefined is what JavaScript produces for a missing value, while null is what code assigns on purpose. Loose equality treats them as equal to each other, and strict equality tells them apart:
> null == undefined
true
> null === undefined
false
> Number(null)
0
> Number(undefined)
NaN
Common null Gotchas
Reading a property of null throws a TypeError, just like reading one of undefined. Optional chaining with ?. returns undefined instead of throwing:
> const account = null;
undefined
> account.name
Uncaught TypeError: Cannot read properties of null (reading 'name')
> account?.name
undefined
Default parameter values don’t apply to null, only to undefined, so passing null skips the default:
> function greet(name = "guest") { return `Hello, ${name}!`; }
undefined
> greet(null)
'Hello, null!'
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By Leodanis Pozo Ramos • Updated Nov. 4, 2026
