I compare as const assertions and satisfies operator in this post.

as const comes with TypeScript 3.4 and generates literal values for more precise and type-safe code.

satisfies comes with TypeScript 4.9 and generates more specific type and validates given object type so that it can catch possible error.

Notice that as const generates a type with readonly fields. So it is an immutable type.

Use case

Notice that satisfies just generates a type from palette object. As you can see below code, red field type is [number, number, number]

As you can see below code, red field type became string instead of [number, number, number]

Use case

satisfies operator catches unlisted field name usage, or wrong field type.

It is a really good feature coming with TypeScript 5.0. We could infer type of object as general as shown in line 8 in below code, so, to infer more-specific type, we had to add as const as shown in line 11.

TypeScript 5.0 makes it easier with adding const in front of type parameter declaration in line 13 in below code.

Use case

Assume that Person type has hobbies , and i just want to infer passed values from hobbies field.