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And that is it for interfaces and classes in this module we had a detailed look at classes and what

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we can do there.

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Classes in typescript in the end just build up on classes for JavaScript and I already summarized those

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a little bit earlier in this module.

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Interfaces are a different thing.

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They only exist in typescript very pure types with feature helping you to write clear clearly structured

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and very explicit code they can help you to force classes to have certain features or objects in general

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to have a certain structure.

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They can be used as a function type as you learned.

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They allow for optional properties and all the four optional methods by the way.

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If you add a question mark after the method name so that is something you can use.

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And as you just saw when being compiled after fulfilling their role of allowing typescript to check

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your code nothing is emitted for these interfaces.

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The code is simply dumped.

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Interfaces nonetheless are a powerful feature to force your classes or your objects to have a certain

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structure and to clearly describe your idea of how an object should look like.

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Now as you learned you mostly can replace them with custom types if you wanted to.

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You can also implement custom types but it simply is more common to use an interface for Dad to use

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an interface if you want to describe an object and if you want to implement it all div for historic

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reasons.

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Because in the early days of typescript custom types couldn't be implemented or used like interfaces.

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Now there is more flexibility but it's still recommended to go for interfaces.

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If you work with objects and if you want to describe their structure will also see them throughout this

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course.

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Over and over again.