There are two main tools to declare the shape of an
type Puppy = {
You can add fields to already existing types. object: interfaces and type aliases. Yall, let's talk about: type vs interface Ever wondered if you should use type (Type Alias) or interface in Typescript? it's possible to intermix their use too. // In the other case a type cannot be changed outside of
This article focuses on the various aspects of Interfaces and Types and when to use them. Both of the constructs will give the same output. are that interfaces are open and type aliases are closed. There are some basic types in TypesSript using Interfaces and Types are constructed.if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[580,400],'delftstack_com-medrectangle-4','ezslot_2',112,'0','0'])};if(typeof __ez_fad_position!='undefined'){__ez_fad_position('div-gpt-ad-delftstack_com-medrectangle-4-0')}; The following code segment shows an example of an interface in TypeScript. If you found this post interesting please leave a on this tweet and consider following my journey about #webperf, #buildinpublic and #frontend matters on Twitter. type BirdType = {
}
Interfaces and classes in TypeScript act as static blueprints and therefore can not extend type aliases with union operators in the type definition. DelftStack articles are written by software geeks like you. Proper tools and IDE supporting TypeScript can suggest code completions, detect errors in types, automatically fix errors, and much more. Interfaces are preferred when designing an API library or declaring objects. colour: string;
colourful: false;
wings: 2;
toys: number;
type Robin = { nocturnal: false } & BirdInterface;
its declaration. A single function call can return an array of values and functions, that are destructured and can be used as fully typed variables: const [name, setName] = useState(''). This can be confusing for anyone working with TypeScriptbeginner or seasoned programmer. // That said, we recommend you use interfaces over type
wings: 2;
interface Kitten {
messages when working with interfaces like Chicken. Simon Wicki is a Freelance Developer in Berlin. // Depending on your goals, this difference could be a
In this post youll quickly see what Typescript feature is possible to implement as Type Alias or Interface. 
// One major difference between type aliases vs interfaces
const bird2: BirdInterface = { wings: 2 };
Interfaces declared multiple times would merge into one, while multiple declarations of Type Aliases will give errors.
If youve used hooks in react, then you know the usefulness of tuples.
// They both support extending other interfaces and types. messages.
A simple typo in the attribute name will fail the compilation and prevent run-time errors. to the recursive property. Types are preferred more in declaring constants and as return types for functions. string, number and boolean make up the Primitives in Typescript. It becomes useful in the case of the production of a public API so that consumers can make further additions to the API by declaring it again. type Puppy = {
Interface vs Type alias in TypeScript 2.7, Type Alias lets you do it but changes that type to, Interface spits an error that the types are not compatible. Functions can be annotated with Parameter Types and Return Types. interface Kitten {
type Owl = { nocturnal: true } & BirdType;
thread is a good place to start:
const bird3: BirdInterface = bird1;
aliases. TLDR: You dont care about each difference? jQuery library for auto completion) onto an existing type (e.g.
I stayed brief and spicy to give the post an overview character. const bird1: BirdType = { wings: 2 }; This means you can extend an interface by declaring it Recursion are simple to use. }; Both ways can cover similar needs. They are very similar, and for the most common cases color: string; }; chicken = owl; I put together a quick overview of TS features that you can or can't type with Type Aliases and Interfaces.
flies: false; } cases around types vs interfaces, this stack overflow act the same. }; So if the extended or intersected key is not the same type: Here are a few useful applications of this: Typescripts equivalent to OR: The type is either x or y or z or as many as you want. If you also would like to contribute to DelftStack by writing paid articles, you can check the, Write console.log Wrapper for Angular 2 in TypeScript, the Similarities of Interfaces and Types in TypeScript, Differences Between Interfaces and Types in TypeScript, Extend an Interface With Nested Properties in TypeScript. Specifically, because you will get better error
Otherwise the TS compiler spits out an error upon searching an endless recursion. interface Peacock extends BirdType { JustWatch. Although intersect and extend are not 100% the same for interface and type alias, I put them together in this example. TypeScript helps prevents run time errors which would be inevitable in the case of JavaScript for wrongly inferred types. However for publicly exposed
purrs: boolean; window). // Because TypeScript is a structural type system, colourful: true; positive or a negative. owl = chicken; For example: Thus to summarize, there are subtle differences to be kept in mind while working with Types and Interfaces in TypeScript. Its useful when you add a new field (e.g. One of the best resources for seeing all of the edge } Now we can implement the same construct with Types. The following code segment shows this. } [1/10] pic.twitter.com/2GQwrwnQ0u. Explore how TypeScript extends JavaScript to add more safety and tooling.
interfaces have a keyword. The following code segments show how this is possible. TypeScript is a programming language maintained by Microsoft and is a superset of JavaScript with support for strong typing. types, it's a better call to make them an interface. TypeScript becomes extremely useful for organizations having large codebases. See how TypeScript improves day to day working with JavaScript with minimal additional syntax. Worked on Web and Mobile apps at Fluent in Vue, Angular, React and Ionic. What should you use? non-fiction books. Both Types and Interfaces can extend others, thus supporting the strongly-typed OOP paradigm. } https://stackoverflow.com/questions/37233735/typescript-interfaces-vs-types/52682220#52682220, How to provide types to functions in JavaScript, How to provide a type shape to JavaScript objects, How TypeScript infers types based on runtime behavior, How to create and type JavaScript variables, An overview of building a TypeScript web app, All the configuration options for a project, How to provide types to JavaScript ES6 classes, Made with in Redmond, Boston, SF & Dublin. let owl: Owl = { wings: 2, nocturnal: true }; However, the syntax for extending is different. see how TypeScript can provide terser and more focused For example: Finally, Interfaces in TypeScript support declaration merging, which doesnt work with Type Aliases. If you hover over the following errors, you can interface Chicken extends BirdInterface { Make sure you add the optional ? TypeScript can give all this support with the help of Interfaces and Types. a second time.
Type aliases do this via intersection types, while interface BirdInterface { Passionate about Frontend, tech, web perf & flies: false; The differences arise when type keys appear in both types that you want to extend or intersect from. let chicken: Chicken = { wings: 2, colourful: false, flies: false };
}
Interfaces and classes in TypeScript act as static blueprints and therefore can not extend type aliases with union operators in the type definition. DelftStack articles are written by software geeks like you. Proper tools and IDE supporting TypeScript can suggest code completions, detect errors in types, automatically fix errors, and much more. Interfaces are preferred when designing an API library or declaring objects. colour: string;
colourful: false;
wings: 2;
toys: number;
type Robin = { nocturnal: false } & BirdInterface;
its declaration. A single function call can return an array of values and functions, that are destructured and can be used as fully typed variables: const [name, setName] = useState(''). This can be confusing for anyone working with TypeScriptbeginner or seasoned programmer. // That said, we recommend you use interfaces over type
wings: 2;
interface Kitten {
messages when working with interfaces like Chicken. Simon Wicki is a Freelance Developer in Berlin. // Depending on your goals, this difference could be a
In this post youll quickly see what Typescript feature is possible to implement as Type Alias or Interface. // One major difference between type aliases vs interfaces
const bird2: BirdInterface = { wings: 2 };
Interfaces declared multiple times would merge into one, while multiple declarations of Type Aliases will give errors.
If youve used hooks in react, then you know the usefulness of tuples.
// They both support extending other interfaces and types. messages.
A simple typo in the attribute name will fail the compilation and prevent run-time errors. to the recursive property. Types are preferred more in declaring constants and as return types for functions. string, number and boolean make up the Primitives in Typescript. It becomes useful in the case of the production of a public API so that consumers can make further additions to the API by declaring it again. type Puppy = {
Interface vs Type alias in TypeScript 2.7, Type Alias lets you do it but changes that type to, Interface spits an error that the types are not compatible. Functions can be annotated with Parameter Types and Return Types. interface Kitten {
type Owl = { nocturnal: true } & BirdType;
thread is a good place to start:
const bird3: BirdInterface = bird1;
aliases. TLDR: You dont care about each difference? jQuery library for auto completion) onto an existing type (e.g. I stayed brief and spicy to give the post an overview character. const bird1: BirdType = { wings: 2 }; This means you can extend an interface by declaring it Recursion are simple to use. }; Both ways can cover similar needs. They are very similar, and for the most common cases color: string; }; chicken = owl; I put together a quick overview of TS features that you can or can't type with Type Aliases and Interfaces.
flies: false; } cases around types vs interfaces, this stack overflow act the same. }; So if the extended or intersected key is not the same type: Here are a few useful applications of this: Typescripts equivalent to OR: The type is either x or y or z or as many as you want. If you also would like to contribute to DelftStack by writing paid articles, you can check the, Write console.log Wrapper for Angular 2 in TypeScript, the Similarities of Interfaces and Types in TypeScript, Differences Between Interfaces and Types in TypeScript, Extend an Interface With Nested Properties in TypeScript. Specifically, because you will get better error
Otherwise the TS compiler spits out an error upon searching an endless recursion. interface Peacock extends BirdType { JustWatch. Although intersect and extend are not 100% the same for interface and type alias, I put them together in this example. TypeScript helps prevents run time errors which would be inevitable in the case of JavaScript for wrongly inferred types. However for publicly exposed
purrs: boolean; window). // Because TypeScript is a structural type system, colourful: true; positive or a negative. owl = chicken; For example: Thus to summarize, there are subtle differences to be kept in mind while working with Types and Interfaces in TypeScript. Its useful when you add a new field (e.g. One of the best resources for seeing all of the edge } Now we can implement the same construct with Types. The following code segment shows this. } [1/10] pic.twitter.com/2GQwrwnQ0u. Explore how TypeScript extends JavaScript to add more safety and tooling.
interfaces have a keyword. The following code segments show how this is possible. TypeScript is a programming language maintained by Microsoft and is a superset of JavaScript with support for strong typing. types, it's a better call to make them an interface. TypeScript becomes extremely useful for organizations having large codebases. See how TypeScript improves day to day working with JavaScript with minimal additional syntax. Worked on Web and Mobile apps at Fluent in Vue, Angular, React and Ionic. What should you use? non-fiction books. Both Types and Interfaces can extend others, thus supporting the strongly-typed OOP paradigm. } https://stackoverflow.com/questions/37233735/typescript-interfaces-vs-types/52682220#52682220, How to provide types to functions in JavaScript, How to provide a type shape to JavaScript objects, How TypeScript infers types based on runtime behavior, How to create and type JavaScript variables, An overview of building a TypeScript web app, All the configuration options for a project, How to provide types to JavaScript ES6 classes, Made with in Redmond, Boston, SF & Dublin. let owl: Owl = { wings: 2, nocturnal: true }; However, the syntax for extending is different. see how TypeScript can provide terser and more focused For example: Finally, Interfaces in TypeScript support declaration merging, which doesnt work with Type Aliases. If you hover over the following errors, you can interface Chicken extends BirdInterface { Make sure you add the optional ? TypeScript can give all this support with the help of Interfaces and Types. a second time.
Type aliases do this via intersection types, while interface BirdInterface { Passionate about Frontend, tech, web perf & flies: false; The differences arise when type keys appear in both types that you want to extend or intersect from. let chicken: Chicken = { wings: 2, colourful: false, flies: false };