The typeof() operator returns the data type of the argument.

A useful command if you need to find out, for example, what type of data the form returns on the site.

Y typeof() there are two syntax options:

Syntax of the typeof x operator

Syntax of the function typeof(x)

Both syntaxes work the same way.

typeof() returns a string that contains the data type.

typeof undefined // "undefined"

typeof 0 // "number"

typeof 1n // "bigint"

typeof true // "boolean"

typeof "foo" // "string"

typeof Symbol() // "symbol"

typeof {} // "object"

typeof null // "object"  

typeof function(){} // "function" 

You need to pay attention to null, as it is not an object of a separate data type. This is an officially recognized error in the language.