One post tagged with "typescript"

Properties defined on an object that are not expressed by the type of the object are called excess properties.

Here's an example:

type Person = {
	firstName: string
}

const person: Person = {
	firstName: "Filip",
	lastName: "Tammergård", // ⛔️ Object literal may only specify known properties, and 'lastName' does not exist in type 'Person'.
}

In this case, TypeScript makes it clear that lastName is not defined in the Person type and is therefore not allowed.