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Type vs Interface in Typescript

vicradon profile image Osinachi Chukwujama ・1 min read

Typescript offers two ways to define types. Either Type-Aliases or Interfaces. The choice of which to use depends on the complexity of the type you want to define.

For most cases, a Type-Alias would get the job done. Most things offered by interfaces are also available in the Type-Alias API. Let's see an example

Extending types

With interfaces, you could do this

interface Human {
  height: number,
  age: number,
  name: string
}

interface Woman extends Human {
  canConcieve: boolean
}

Applying the same logic using Type-Aliases would be

type Human = {
  height: number,
  age: number,
  hairColor: string
}

type Woman = {
  canConcieve: boolean
}

const Chisom: Human & Woman = {
  height: 1.5,
  age: 20,
  hairColor: 'brown',
  canConcieve: true
} 

People who prefer functional-style programming to Object-Oriented Programming may find Type-Aliases to be a better approach. Loosely defined types that can be combined.

Discussion

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rconr007 profile image
rconr007

Thanks this seems very handy.

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Ulisses Cavalcante

Nice approach.

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aiosifelis profile image
Andreas Iosifelis

Very useful. Thanks!

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John Peters

Don't forget the Class. No explicit interface needed but acts just like an interface.