Primitive Types

There are 7 primitive types:

• undefined
• null
• Boolean
• Number (double-precision 64-bit binary format IEEE 754)
• String
• BigInt
• Symbol

Primitive types are immutable.

We'll look at undefined and null when we cover nullability. BigInt and Symbol are less common.

Primitive values

We declare primitive types using... primitive values (i.e. literals).

Constructor functions

It's also possible to instantiate the built-in types using their constructors — however, this is relatively uncommon and not idiomatic for common usage.

Standard library methods

We use standard library methods for manipulating primitives. These are available as methods on each instance.

JavaScript uses autoboxing to make these methods available even on literal values.

Type casting

There are library methods for casting strings to numbers and vice versa: