By u sing scalar types (object, …) or any, we prevent TypeScript to infer the return type.. To overcome this problem, we’re gonna use generics. Let's find out Create a new npm project, install Fastify, and install typescript & node.js types as peer dependencies: npm init -y npm i fastify npm i -D typescript @types/node; Add the following lines to the "scripts" section of the package.json: TIP: You can call the generic parameter whatever you want. Generics provide a way to make components work with any data type and not restrict to one data type. However, using generics does have some constraints. All this does is take a type … These parameters are not restricted to a certain type. Set the argument equal to 200: If you would like to see the results of this code, you can include console.log statements to print result and result2 to the console: In the end, your code should look like this: Use ts-node to run this TypeScript code in the console: The code renders without error. Stack Overflow for Teams is a private, secure spot for you and instead of specifying the generic type, you specify the corresponding constructor reference of that generic type): The type new (...args: any[]) => T simply says: a newable type (i.e. The Omit type lets us create an object type that omits specific properties from another object type: How to convert a string to number in TypeScript? Instead, you can supply the constructor reference, which you can also use to infer the generic type (i.e. If there are many parameters in a function, you can use different letters to denote the types. It’s common to use single-letter names for generic type parameters, but it doesn’t have to be that way. Who must be present at the Presidential Inauguration? Here’s an example of the same function being used for two different data types: Note that, in this example, the same function is being repeated for number and string types. TKey and TValue (conventional to prefix with T as generics are … You don’t have to only use T: This function takes 3 parameters, args1, args2, and arg3, and returns args3. In this article, we learn about index types. Fetch Wrapper in TypeScript. Think of Box as a template for a real type, where T is a placeholder that will get replaced with some other type. For the arguments, include a string, a number, and boolean held within parentheses: This will return the third argument, false. We'd like to help. Since a composable function is of arity 1 (arity means accept 1 parameter), then I can write a generic type for these functions as follows: type ArityOneFn = (arg: any) => any; Now I can write the type of the compose function rest argument as follows: Classic short story (1985 or earlier) about 1st alien ambassador (horse-like?) Up until this point, you’ve created functions and classes using generics. Hacktoberfest So customArray can be an array of numbers, booleans, or strings. As with almost any programming concept, the idea of Generics has been around for quite some time. How to get the type of T from a member of a generic class or method? It now needs length as a required parameter. This post is not meant to be an introduction to Generics. Create an instance of customArray for number and string types. TypeScript - Generic Classes. This. Note: Type variables are also referred to as type parameters and generic parameters. Accessing this getLength function with an argument that doesn’t have a length parameter will show an exception message. To create type-safe generics, you will need to use Type parameters. Asking for help, clarification, or responding to other answers. Eliminate type castings. TypeScript Generics is a tool which provides a way to create reusable components. Let's see why we need Generics using the following example. I'm trying to get the type of a class which is calling the generic method. In this post, I want to explore how we can benefit from generic parameter defaults by migrating the following React component from JavaScript (and JSX) to TypeScript (and TSX): In this example, we will develop a generic Stack class. Nullable type as a generic parameter possible? 8 min read. But there’s a catch—using the any type means that the fun function can accept any data. How to make one wide tileable, vertical redstone in minecraft, I found stock certificates for Disney and Sony that were given to me in 2011. In this post, I want to explore how we can benefit from generic parameter defaults by migrating the following React component from JavaScript (and JSX) to TypeScript (and TSX): It results in a blank http Fastify server. If a jet engine is bolted to the equator, does the Earth speed up? Here we made on into a generic method. Declare a variable called numObj set equal to an instance of customArray for number types: Use the addItem method to add the number 10 to numObj: Since customArray is generic, it can also be used to create an array of strings. Types are documentation, and type parameters can have descriptive names. It just doesn’t work. Step 2 — Creating Type-Safe Generics. TypeScript provides handy built-in utilities that help to manipulate types … When TypeScript sees Box, it will replace every instance of T in Box with string, and end up working with something like { contents: string }. In the next step, you explore a different option for creating type-safe generics. How were four wires replaced with two wires in early telephone? Generics provide a way to make components work with any data type and not restrict to one data type. Any other interface/type (like the one defined below) will not work in this way either. How many dimensions does a neural network have? How to disable metadata such as EXIF from camera? Types provide a way to describe the shape of an object, providing better documentation, and allowing TypeScript to validate that your code is working correctly. In this post we'll take a look at a couple more advanced features of generics – generic constraints and default values. There is a solution to this problem—creating generic constraints. In this post we'll take a look at a couple more advanced features of generics – generic constraints and default values. That said, we can now use the interface and provide different types as argument. It will not show any error message. TypeScript's generic types are very powerful – mostly because TypeScript was created to statically type dynamic JavaScript code. TypeScript - Generic Classes. Hub for Good nameof operator. TypeScript Generics. then (x => x. toUpperCase ()) This will be discussed in the next step. Using the any type will allow you to opt-out of type-checking. TypeScript's generic types are very powerful – mostly because TypeScript was created to statically type dynamic JavaScript code. class MyClass { getName() { return (this).constructor.name; // OR return (this as any).constructor.name; } } // From outside the class: var className = (new MyClass()).constructor.name; // OR var className = (new MyClass() as any).constructor.name; console.log(className); // Should output "MyClass" // From inside the class: var instance = new … TypeScript provides dedicated type syntax for arrays to make it easier for you to annotate and document your code. Tidy TypeScript: Name Your Generics . Typescript generics are a built in language feature using the same principles of generics in other languages like C#, ... Notice that the ItemType is the generic parameter name. Although using the any type is a way to make your TypeScript code more generic, it may not always be the best option. Making statements based on opinion; back them up with references or personal experience. Benefits of TypeScript generics. Generic Parameter Defaults in TypeScript June 2, 2017. Stefan Baumgartner Type parameters are defined by T or . The following are benefits of TypeScript generics: Leverage type checks at the compile time. This is because T, U, and V are used as generic types for the fun function’s parameters. Want to guarantee type safety of "stringly typed" property names in your code? Generics offer a way to create reusable components. For Ex: getAll i want to get the type SubscriberData inside that method. 1) Generic function in TypeScript : We can make a function generic in TypeScript by using <> brackets. You were able to accomplish this by using generic types. In C# we can define a generic type argument and instantiate this type at runtime: public class Factory {public T Create < T >() where T: new {return new T ();}} var factory = new Factory (); var person = factory. This can be done, although a little differently to other languages. The generic type parameter is specified in angular brackets after the name of the class. TypeScript has some powerful features that enable easy building of scalable JavaScript applications. Note: Type variables are also referred to as type parameters and generic parameters. Step 4: Let’s write the generic compose function in typescript to get better type checks. Sign up for Infrastructure as a Newsletter. In JavaScript, this doesn't work: typeof obj return "object" or something else, but never the name of the class. Generics is a powerful feature that allows our code to abstract away from the specific types being used, making it more reusable and generic without giving up on type-safety. declare const backpack: Backpack ; // object is a string, because we declared it above as the variable part of Backpack. Written by Alexander Eckert on Sunday, July 12, 2020 — ☕ 4 min read. TypeScript 2.3 implemented generic parameter defaults which allow you to specify default types for type parameters in a generic type.. Now the generic class customArray is complete. Create a variable called result3 and assign it to fun. If you hover on the getTuple function name in your IDE, you will see the below type signature of the function. Inside the angle brackets are the “type parameters”. typescript - Is it possible to get the type name of a generic type? The type parameter in angle (<>) brackets are used, as with functions. interface Backpack < Type > {add: (obj: Type) => void; get: => Type;} // This line is a shortcut to tell TypeScript there is a // constant called `backpack`, and to not worry about where it came from. It returns a promise of whatever type you pass in: This time, we take them to a higher level. To create type-safe generics, you will need to use Type parameters. Following the Don’t-Repeat-Yourself (DRY) principle is important when it comes to writing dynamic and reusable code. Create a class that takes both number and string inputs and creates an array with those inputs. The best solution I came up with, is to pass the generic type as method argument and add a generic type argument which will be inferred from the method argument and thus must not be declared: class Person { firstName = 'John'; lastName = 'Doe'; } class Factory { create(type: (new () => T)): T { return new type(); } } let factory = new Factory(); let person = factory.create(Person); … const nameof = (name: keyof T) => name; . Typescript generic rest parameters and tuple types are powerful type constructs when working with higher order functions. Working with generics # TypeScript’s generics syntax is available wherever there’s a type that can be generic: /** @type PromiseLike */ let promise; // checks. Inside this brackets, we pass our type. Instead, you can supply the constructor reference, which you can also use to infer the generic type (i.e. A stack is a data structure that works on the last-in-first-out (or LIFO) principle. In ES6, you can use Function.name to get the name of a function (documentation). typescript - Optional generic type; TypeScript: Is it possible to get the return type of a generic function? To see this drawback in action, write a function called getLength that will return the length of the function’s argument: This function will work as long as the passing type has a length property, but data types that don’t have a length property will throw an exception. How do I use reflection to call a generic method? Podcast 305: What does it mean to be a “senior” software engineer. Generics used only once are no better than an assertion in terms of type safety. How do I get a class instance of generic type T? To see this in practice, apply the any type to the previous code example: Swapping number and string types to the any type makes the function generic. If you have more than one generic argument try to use meaningful names e.g. If anybody has ideas about similar ways to achieve the same result whilst working within the boundaries of TypeScript's existing type system, let's get … When i tried this getting the following exception. TypeScript supports generic classes. How to get the type of T inside generic method in Typescript? They denote the data type of passed parameters to a class, interface, and functions. So, components can be called or used with a variety of data types. If you have an instance of a class, you can use the name of the constructor function to identify it. To see this, you can use a console.log statement: Run the ts-node command to see your console.log statement output: Now you can create generic types for functions with multiple parameters. `then` is available, and x is a string promise. To learn more, see our tips on writing great answers. Efficient way to JMP or JSR to an address stored somewhere else? Similarly to string literal types, these types disappear and turn into string through a process called widening if we assign one of these values to a mutable variable. What language(s) implements function return value by assigning to the function name. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Why does G-Major work well within a C-Minor progression? It allows users to consume these components and use their own types. Do Typescript generics use type erasure to implement generics? Generics can help you to write generalized methods instead of writing and repeating the same block of code, as in the above example. : function demo1(param: T): T {return param;} With generics, you can write dynamic and reusable generic blocks of code. In this tutorial, you successfully integrated generics into your TypeScript functions and classes. The TypeScript language doesn't include a nameof operator like in C#, but you can make one yourself easily:. SomeGeneric is not a value, it is a type in and of itself. Benefits of TypeScript generics. You also included constraints for your generics. It’s also important to know how to create generics for functions with multiple parameters of many different types. ; Defined a type guard isPrimitive which basically defines which types we are going to print out of the box. const nameof = (name: keyof T) => name; . Unfortunately, generic type arguments are not available at runtime this way, they'll always yield the runtime equivalent of a simple Object type. The following are benefits of TypeScript generics: Leverage type checks at the compile time. Generics in TypeScript is almost similar to C# generics. Generics also support default values and constraints. The argument will be the Hello World string: Try using the fun function with the number type. Placing the type parameter on the class allows you to develop methods and properties that work with the same type. Mapped types work well with other features in this type manipulation section, for example here is a mapped type using a conditional type which returns either a true or false depending on whether an object has the property pii set to the literal true: Naming generic type parameters # Most generic type parameters start with the letter T. Subsequent parameters go along the alphabet (U, V, W), or are abbreviations like K for key. SomeGeneric is not a value, it is a type in and of itself. How can we use fetch to simplify the code for making HTTP requests taking full advantage of TypeScript's type system. We’re using T as our generic type, this generic type allows us to work with a variety of types instead of a single one. A common question that crops up from time to time on TypeScript forums is how to check the type of a class at runtime using TypeScript. TypeScript supports generic classes. This quality is one of many reasons generics are more powerful than simply using the any type. A generic class can have generic fields (member variables) or methods. Google Gson - deserialize list object? in .NET, it's easy to get the class name of an object using obj.GetType().Name. Eliminate type castings. A stack is a data structure that works on the last-in-first-out (or LIFO) principle. Not 0, not 2, not 3, not 4. This call has a length property, and your function will work well. It creates a component that can work with a variety of data types rather than a single data type. The generic type parameter is specified in angular brackets after the name of the class. If you would like to learn how to work with TypeScript in VS Code, this How To Work With TypeScript in Visual Studio Code article is a great place to start. Using Generic types. Familiarity with writing functions and classes in TypeScript. (generic type), Type definition in object literal in TypeScript. Allow you to implement generic algorithms. T stands for Type, and is commonly used as the first type variable name when defining They are similar in concept to generics in Java. The Fetch API is a native browser function that provides an interface for fetching resources asynchronous across the network. It contains all the code we've seen and the final demo shown in the gif above. Two weeks ago I wrote about Conditional React prop types with TypeScript.Last week we learned about Polymorphic React components in TypeScript.And today we’re continuing the React + TypeScript theme, this time focusing on creating generic … You might be wondering here, ‘but why T?’ T stands for Type, and it’s commonly used by TypeScript to refer to the first type variable name. You can access the constructor reference of a class in a class decorator, a property in a property (or accessor) decorator, or a parameter in a parameter decorator (using reflect-metadata). We’re using T as our generic type, this generic type allows us to work with a variety of types instead of a single one. This article opts to use the term type variables, coinciding with the official Typescript documentation. To see the results of your code, create a console.log statement for both numObj and strObj: After running ts-node, this is the output you will receive: You used the customArray class for both number and string types. Write for DigitalOcean rev 2021.1.20.38359, Stack Overflow works best with JavaScript enabled, Where developers & technologists share private knowledge with coworkers, Programming & related technical career opportunities, Recruit tech talent & build your employer brand, Reach developers & technologists worldwide, The type system is lost at compile time, so it won't be available at runtime. TypeScript generics are an advanced feature of TypeScript that allows for parameterizing existing types. To do this, you will first need to create an interface called funcArgs and define a length property: Now, change the getLength function and extend it to include the funcArgs interface as a constraint: You’ve created a generic constraint using an interface. You get paid, we donate to tech non-profits. In other words, Box and our earlier StringBox work identically. If anybody has ideas about similar ways to achieve the same result whilst working within the boundaries of TypeScript's existing type system, let's get … Create a method called getItems that returns the customArray array: Create a method called addItem that adds new items to the end of the customArray array: The arr: T[] argument means that the items within the array can be of any type. site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. The syntax is basically postfixing [] to any valid type annotation (e.g. Include the types to fill in the T, U, and V generic types. Returning to the fun function, use T to make your generic function type-safe: As a result, fun is now a type-safe generic function. Typescript: Ensure that a generic type has a certain property; Get constructor/instance from generic type in TypeScript Thanks for contributing an answer to Stack Overflow! The TypeScript language doesn't include a nameof operator like in C#, but you can make one yourself easily:. Supporting each other to make an impact. Although using the any type is a way to make your TypeScript code more generic, it may not always be the best option. In the next step, you explore a different option for creating type-safe generics. Join Stack Overflow to learn, share knowledge, and build your career. Here, we pass in two parameters: T and U, and then use them as type annotations for the properties. DigitalOcean makes it simple to launch in the cloud and scale up as you grow – whether you’re running one virtual machine or ten thousand. nameof operator. How to instantiate a generic type in TypeScript. The cool thing now is, when defining a player and its animal, we can only define one of the animals. However, any is not type-safe. This doesn't mean you cannot get the name of a class in JS. Syntactically, type generics are signalled by the use of angle brackets on function, class, and type declarations. Here's a Typescript Playground which you can have fun with. When a user calls with the string "firstNameChanged', TypeScript will try to infer the right type for K.To do that, it will match K against the content prior to "Changed" and infer the string "firstName".Once TypeScript figures that out, the on method can fetch the type of firstName on the original object, which is string in this case. Writing types can be optional in TypeScript, because type inference allows you to get a lot of power without writing additional code. Get the latest tutorials on SysAdmin and open source topics. Working for client of a company, does it count as being employed by that client? You get paid; we donate to tech nonprofits. Allow you to implement generic algorithms. To test this type-safe generic function, create a variable named result and set it equal to fun with a string type parameter. I have a problem with generics in TypeScript. The 'typeof' operator is not meant to describe the constructor of a type, but rather the type of a value. You might be wondering here, ‘but why T?’ T stands for Type, and it’s commonly used by TypeScript to refer to the first type variable name. Using Generic types. Previously, we’ve discussed the basics of TypeScript Generics. In this article, you will integrate generics into your TypeScript code and apply them to functions and classes. Let’s break down what’s happening here: We defined the helpers objectValues which provides us a better way to get the object values with the correct typing. To successfully complete this tutorial, you will need the following: Sometimes, you may want to repeat the same block of code for different data types. Basically: you get a combination of types that aren’t as strict as you’d like and broken inference. There is a type called any, which you can use to achieve the same effect as generics in your code. your coworkers to find and share information. To push some more parameters to the http call and alter http url by checking this condition based on a type. Generic Parameter Defaults in TypeScript June 2, 2017. All this does is take a type … Like functions, generics can be used with classes and interfaces as well. Then the type is used throughout the class for defining methods and properties. e.g. A generic type can receive several arguments. It allows you to safely do any array manipulation that you would normally do and protects you from errors like assigning a member of the wrong type. This means that using any can give you an exception. Since a composable function is of arity 1 (arity means accept 1 parameter), then I can write a generic type for these functions as follows: type ArityOneFn = (arg: any) => any; Now I can write the type of the compose function rest argument as follows: :boolean[]). A generic class can have generic fields (member variables) or methods. When the type on the left of the extends is assignable to the one on the right, then you’ll get the type in the first branch (the “true” branch); otherwise you’ll get the type in the latter branch (the “false” branch).. From the examples above, conditional types might not immediately seem useful - we can tell ourselves whether or not Dog extends Animal and pick number or string! Furthermore, you also extended the getLength function with this interface. This is the basic rule to define generics in TypeScript or in any other programming language. TypeScript 2.3 implemented generic parameter defaults which allow you to specify default types for type parameters in a generic type.. I'm trying to get the type of a class which is calling the generic method. This post is not meant to be an introduction to Generics. The Omit Helper Type in TypeScript March 28, 2020. As a result, you are losing type safety as well. But there is a drawback to using generics. That said they do provide convenience to your API. How can I hit studs and avoid cables when installing a TV mount? Contribute to Open Source. Of type-checking it creates a component that can work with any data type of passed to. Than one generic argument try to use the name of an object obj.GetType. Similar in concept to generics on Sunday, July 12, 2020 — 4..., see our tips on writing great answers of Box as a for. To any valid type annotation ( e.g TypeScript can also infer generic types by its usage defining methods properties! Name of the function in two parameters: T and U, build! In and of itself the syntax is basically postfixing [ ] to any valid annotation! Parameter in angle ( < > brackets in the T, U, V when have! You may be interested in learning how to create type-safe generics mean you can also use to the... Demo shown in the gif above V when you have an instance of generic... The same effect as generics in your IDE, you can also infer generic by... Syntax is basically postfixing [ ] to any valid type annotation (.! Infer generic types using obj.GetType ( ).Name do provide convenience to your API ( like the one below! Then ` is available, and x is a type … TypeScript now. Number type: T and U, and classes IDE, you will also learn mapped and... Almost similar to C # generics string: try using the any will! Post your Answer ”, you can make one yourself easily:, coinciding with the TypeScript., those couldn ’ T be compatible with our new template string types instead... Help to manipulate types … benefits of TypeScript generics to develop reusable, generalized, type-safe! Turn, those couldn ’ T have to be that way speed up on function create! Used throughout the class name of an object using obj.GetType ( ).. Property, and type parameters in a function that loads a json response for type! The “ type parameters, but is being used as generic types senior ” engineer. X is a lot going on here, we ’ ve created functions and classes using generics can help to! Type safety of `` stringly typed '' property names in your code provide convenience to your.! Defining methods and properties Fetch to simplify the code for making http requests taking full advantage of TypeScript to. For type parameters in a function generic in TypeScript 4.2, template string expressions now always start out template... Also extended the getLength function with the official TypeScript documentation aren ’ T a. Of T from a member of a generic class can have fun with TypeScript by using types... In many situations and build your career horse-like? be generic too use Function.name to get better type at. 'S type system to identify it class/constructor ) that returns the generic type magic system when no character an. Using any can give you an exception try using the any type will allow you to write generalized instead... It 's easy to get the type of a value does G-Major work.... Documentation ) typescript get generic type name names e.g a single data type obj.GetType ( ) by that?! Template for a real type, where T is a tool which a! The corresponding class/constructor for the fun function ’ s common to use name!, U, and string literal types “ type parameters in a function that loads a json.. Being used as generic types for the fun function with the number type parameter. Writing great answers in two parameters: T and U, and classes using generics ” you... Our tips on writing great answers “ type parameters generic argument try to use type parameters, but being. Of Box as a template for a real type, but you also. Typescript, because type inference allows you to opt-out of type-checking how to add constraints to generics you. Combination of types that aren ’ T have ambient type definitions type declarations generics! The function better type checks those inputs concept, the corresponding class/constructor for the method. To use single-letter names for generic type parameters can have fun with a string type parameter in (... Spurring economic growth is one of many reasons generics are an advanced feature TypeScript. Other answers this example will get you up and running with Fastify TypeScript... That aren ’ T have a length property, and classes into your TypeScript code and apply them a. Way to JMP or JSR to an address stored somewhere else logo © 2021 Exchange! Result and set it equal to fun with inside generic method that enable easy building of scalable JavaScript.. It mean to be a “ senior ” software engineer ) brackets the! See our tips on writing great answers ` is available, and string types ever differ greatly from typescript get generic type name score. To classes, interfaces, and classes, reducing inequality, and type parameters, rather! Variables, coinciding with the number type when it comes to writing dynamic and reusable generic blocks code! Type ( i.e write the generic type ), type generics are signalled by the of. What does it count as being employed by that client in concept to generics by using.! Parameters are not restricted to a higher level: now, your array that takes both number and string.! Why does Kylo Ren 's lightsaber use a cracked kyber crystal I want guarantee... The network using interfaces learn how to disable metadata such as EXIF from camera share... Although using the fun function with the official TypeScript documentation the use of angle on. 'S type system how do I use reflection to call a generic type, does the Earth speed up rest! Postfixing [ ] to any valid type annotation ( e.g Hello World:. 1St alien ambassador ( horse-like? reference, typescript get generic type name you can apply generics in TypeScript using! Api is a solution to this problem—creating generic constraints concept, the corresponding for. String types implemented generic parameter defaults which allow you to specify default types for properties. Of code it may not always be the best option Kylo Ren 's lightsaber use a cracked crystal! [ ] to any valid type annotation ( e.g type and not restrict to one data type for of. An array of numbers, booleans, or responding to other languages any data type in concept to generics TypeScript..., where T is a type, where T is a type guard isPrimitive which basically defines which we. Allow you to opt-out of type-checking ) ever differ greatly from the score. No character has an objective or complete understanding of it our new string... I hit studs and avoid cables when installing a TV mount the official TypeScript documentation will generics... Index types generics are more powerful than simply using the any type means that using any can give you exception... Your function will work well within a typescript get generic type name progression mapped types and use their types. One generic argument try to use single-letter names for generic type equal to with. Were able to accomplish this by using generic types by its usage generic Stack.... Some other type almost any programming concept, the keyof keyword, and functions you hover on the (! Write generalized methods instead of writing and repeating the same block of code, as in gif. Typescript - optional generic type and set it equal to fun with TypeScript that allows for parameterizing existing.! Only refers to a certain type not restrict to one data type of inside. Parameters ” that provides an interface for fetching resources asynchronous across the network take them a. Of TypeScript generics to develop reusable, generalized, and classes using generics can generic! Studs and avoid cables when installing a TV mount, we will develop a Stack! You can now use the name of a company, does the Earth speed up it. More powerful than simply using the following example with some other type are structured we generics! Spot for you to get the type of a type in and of itself Earth up! T typescript get generic type name a member of a class that takes in items of types... Use a cracked kyber crystal into your TypeScript functions and classes it creates a that... Specified in angular brackets after the name of the class to specify default for... Type annotation ( e.g keyof T ) = > x. toUpperCase ( ).! Native browser function that provides an interface for fetching resources asynchronous across the network work. Basically postfixing [ ] to any valid type annotation ( e.g below ) will not work this... In JS use to infer the generic compose function in TypeScript to get the class name of an object obj.GetType... T > ( name: keyof T ) = > name ; working on improving health and,. Do I get a combination of typescript get generic type name that aren ’ T have a parameter... Interface, and type-safe functions, classes can be an introduction to in... Not work in this article, you can have descriptive names useful in many situations this way either an.... The last-in-first-out ( or LIFO ) principle Good Supporting each other to make an impact, we about. Health and education, reducing inequality, and type-safe functions, interfaces and... That allows for parameterizing existing types need generics using the any type will allow you to opt-out type-checking.