CODEWITHSUNDEEP
typescriptinterface
Tony
Tony

Reputation: 38341

How to intentionally define an "empty interface" in typescript

TypeScript allows checking for checking unknown properties. The following 

interface MyInterface {
  key: string
}

const myVar: MyInterface = {
  asda: 'asdfadf'
}

will fails with

Type '{ asda: string; }' is not assignable to type 'MyInterface'.
Object literal may only specify known properties, and 'asda' does not exist in type 'MyInterface'.

However, this statement will compile without any issue. Empty interface will accept any value

interface EmptyInterface {
}

const myVar: EmptyInterface = {
  asda: 'asdfadf'
}

However, what if I actually want to define type for an empty object that may not have any properties? How can I accomplish that in typescript?

Upvotes: 4

Views: 5402

Answers (1)

Titian Cernicova-Dragomir
Titian Cernicova-Dragomir

Reputation: 249466

To define an interface that never has any members, you can define an indexer that returns never

interface None { [n: string]: never } 
// OK
let d2 : None = {

}
let d3 : None = {
    x: "" // error
}

Upvotes: 9

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