In Typescript, what is the difference between type and interface?

Issue

What are the differences between the following?

type Foo = { 
    foo: string 
};
interface Foo {
   foo: string;
}

Solution

Interfaces can be extended

interface A {
  x: number;
}
interface B extends A {
  y: string;
}

and also augmented (the so-called declaration merging)

interface C {
  m: boolean;
}
// ... later ...
interface C {
  n: number;
}

Type aliases, however, can represent some things interfaces can't

type NumOrStr = number | string;
type NeatAndCool = Neat & Cool;
type JustSomeOtherName = SomeType;

So in general if you just have a plain object type, as shown in your question, an interface is usually a better approach. If you find yourself wanting to write something that can't be written as an interface, or want to just give something a different name, a type alias is better.

Answered By - Ryan Cavanaugh