How to define a hash with enum keys in Typescript TypeScript map with keys having multiple types, Use an object as a map's key in the value. Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned. Does air in the atmosphere get friction due to the planet's rotation? By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Just type. Java enums are a special kind of Java class used to define collections of constants. Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned. Add a key/value pairs to the map. What's the significance of a C function declaration in parentheses apparently forever calling itself? Tnx. Which field is more rigorous, mathematics or philosophy? For older versions of TypeScript: You can convert an enum value to a string using the enum 's indexer: const messageTypeAsString = MessageType [MessageType.email]; Going the other way works too: const messageType: MessageType = MessageType [messageTypeAsString]; As far as I know there is no way to automate this conversion when serializing . How to use array.map with tuples in typescript? A simple solution using the native Record utility. map enum key literal value. I get the error 'is missing the following ' with each enum value. Does air in the atmosphere get friction due to the planet's rotation? Sometimes, the code inside the for loop will throw an error. Get an Enum Key by Value in TypeScript | bobbyhadz Adding salt pellets direct to home water tank. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I found it is the easiest solution and, most of the time, I dont need any special behavior that would require an external npm library. What should I do? Connect and share knowledge within a single location that is structured and easy to search. When using 'typeof', it looks like, a key in my object was created from a key of an enum, not a value of this key. Introduction In TypeScript, enums, or enumerated types, are data structures of constant length that hold a set of constant values. What's it called when multiple concepts are combined into a single problem? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. If you create a new array with the same elements, it would not consider it to be equal to any existing one. Thank you for this interesting solution, it works but for this simple problem I don't want to extend the default type definitions. Why is that so many apps today require MacBook with a M1 chip? Yours is different I believe. Type 'string' is not assignable to type '"ACH" | "Wire" | "Check" | "Credit"'. Proving that the ratio of the hypotenuse of an isosceles right triangle to the leg is irrational, Most appropriate model fo 0-10 scale integer data. You are applying your assertion at the wrong place. JavaScript, however, does not have the enum data type, but they've been available in TypeScript since v2.4. that looks good, but my problem as that all of your, @SudoPlz I'd suggest opening up a new question for that. Allow "T extends enum" generic constraint #30611 - GitHub Apologize for not seeing this sooner because it's such an old question, but yes, this is what I eventually did and it is absolutely the correct answer. I would like to be able to add a new key to the Map without being forced to change the method. The advantage of using this structure is: This is how you initialize a map in TypeScript: While using the Map object you have access to methods with explicit names that are easier to understand to new developers. Are glass cockpit or steam gauge GA aircraft safer? Where to start with a large crack the lock puzzle like this? Which is rational and make sense to leave generic type as class type. So unless you have a real need for such a "generic" function, make typesafe functions for the individual enum types (or a union type like E1|E2|E3) that you actually need. Connect and share knowledge within a single location that is structured and easy to search. Let's assume that you've got a list of integrations, that you've stored in an enum: And you've got some API that returns only boolean info about available integrations: You could, of course, write an interface for that response, using keys that you've declared before in enum. Pros and cons of "anything-can-happen" UB versus allowing particular deviations from sequential progran execution. Correct way to map through tuple type parameter. How to declare a generic type with same keys as an enum? They also allow us to specify a list of values for a particular collection set or type. (Ep. to get: It was working fine, until I added the line at the end of the code to modify the object after its first creation. Can enum be used as a key type instead of only number or string? To learn more, see our tips on writing great answers. Using the Record<Keys, Type> utility. Mapping with enum key type and literal value type gives not - GitHub Using string enum as Map keys Ask Question Asked 3 years, 9 months ago Modified 3 years, 9 months ago Viewed 1k times 0 I'd like to use a TypeScript enum with string values as Map key: enum Type { a = 'value_a', b = 'value_b' } const values = new Map<Type, number> (); // set a single value values.set (Type.a, 1); This works fine. Share. Returns an iterator object with the values. Use an enum to type an index signature of an interface field? Possible to use enums to restrict values? TypeScript Enum Tutorial - How to Use Enum in TypeScript Each of these constant values is known as a member of the enum. What is the motivation for infinity category theory? I found it surprising until I realised that enums can be thought of as a specialised union type. How to Use enum Keys in TypeScript Interfaces and Types - Plain English And what if you have much more integration types or some other, a more massive amount of data? Use the Object.keys () method to get an array of the enum's keys. At the end of the day, you won't mind little code duplication. The Overflow #186: Do large language models know what theyre talking about? TypeScript | Convert Enums to Arrays - Become A Better Programmer String enum as map key does not work with ReturnType, How to type enum values mapped from key correctly, typescript enum string type an array of Object.keys. That means: This is how you create a map with the immutable library: It is a curated collection of data structures for TypeScript & JavaScript. Now use it to accept any enum as parameter: Thanks for contributing an answer to Stack Overflow! All enum-related solutions are on this page. I would like to use the keys of a Map as type for a method parameter. Enums in TypeScript are just Javascript objects without a common interface or prototype (and if they are const enum, then they are not even objects), so you cannot restrict types to "any enum". Using const string enum as object key produces an indexed type The keys on an enum tend to be titlecase. Rivers of London short about Magical Signature. The keyof keyword is available since Typescript 2.1. How and when did the plasma get replaced with water? Instead of having our component have a prop that inputs a TextType, we can add the definition of TextType itself to our component's interface. An external library (if you need some special behaviors). Does the Granville Sharp rule apply to Titus 2:13 when dealing with "the Blessed Hope? How to specific key to be one of enum keys? Same mesh but different objects with separate UV maps? Summing up the previous answers with some new syntax - a generic typesafe function, which works with numeric enums as well as string enums: function getRandomElementOfEnum<T extends {[key: number]: string | number}>(e: T): T[keyof T] { const keys = Object.keys(e); const randomKeyIndex = Math.floor(Math.random() * keys.length); const randomKey = keys[randomKeyIndex]; // Numeric enums members . Why does this journey to the moon take so long? Hit this odd bug in my code and I can't figure the way to get a constant time lookup from a Map when using a tuple as my key. How to use the map() method with Enums in TypeScript 568 When a customer buys a product with a credit card, does the seller receive the money in installments or completely in one transaction? Yeah of course better than any, but this solution is pretty hard in maintenance. map ( key => enumerable [key]); // we are only interested . Tim Mouskhelichvili - Freelance Developer & Consultant, Create a TypeScript map with an indexed object and a mapped type, Create a TypeScript map with the Record utility type, Create a TypeScript map using the ES6 Map Object, Create a TypeScript map using an external library, The Record type is a pre-defined TypeScript utility type. Conclusions from title-drafting and question-content assistance experiments How can I use a class type as a map key in TypeScript? (I'm haven't worked out in detail how . Are Tucker's Kobolds scarier under 5e rules than in previous editions? How to type enum values mapped from key correctly, Typescript: a Map of keys from a different enums throws an error. Thanks for contributing an answer to Stack Overflow! It should limit the parameter options to the available keys, as stated above. How to handle reverse mapping of string enums with different string literals in typescript? Also easier to update at on place. I can't afford an editor because my book is too long! Asking for help, clarification, or responding to other answers. What is the state of the art of splitting a binary file by size? Why whould you be able to add a property "third"? Use the map() method to iterate over the array, returning an object on each iteration. (Ep. Can allow numeric values outside the enum if you use a numeric enum. @Thilo, No. Asking for help, clarification, or responding to other answers. rev2023.7.14.43533. For the life of my I can't figure this one out. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. when the second value in the tuple depends on the first value) I think it may be possible to use a nested map instead: I don't know whether this would work with Typescript or if there might be other downsides but this seems like a simple to use method to me that will retain the keys as tuples: Thanks for contributing an answer to Stack Overflow! What is the state of the art of splitting a binary file by size? TypeScript: Is it possible to map tuples in a typesafe way? Any idea ? Failed extracting a value from an object using enum as key and casting to enum type (TypeScript) Ask Question Asked yesterday. Making statements based on opinion; back them up with references or personal experience. Get all Enum Values or Names as an Array in TypeScript Access the array of keys at the specific index. Should I include high school teaching activities in an academic CV? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. I can't afford an editor because my book is too long! What is the state of the art of splitting a binary file by size? Is it possible to extend this to have one enum for booleans and another for strings and combine them into a single field list type? So I needed to tell it that the object is going to have some of the enum keys, not all of them. Yet, as a wild guess, either, Nice one but the problem with this solution is that number can be undefined, @walox Typescript had a problem distinguishing, Use Enum as restricted key type in Typescript, github.com/microsoft/TypeScript/issues/13195, github.com/microsoft/TypeScript/pull/43947, How terrifying is giving a conference talk? It can be forced to work by passing value of enum (or any other plain number) but function obviously fails when trying to resolve statement like 2[3]. To get all the keys in an array from a map you need to call the Object.keys() built-in function. Using an object an alternative to enums. Making statements based on opinion; back them up with references or personal experience. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, Nice! Not the answer you're looking for? 4 Answers Sorted by: 52 You can do it as follows: type EnumDictionary<T extends string | symbol | number, U> = { [K in T]: U; }; enum Direction { Up, Down, } const a: EnumDictionary<Direction, number> = { [Direction.Up]: 1, [Direction.Down]: -1 }; Which field is more rigorous, mathematics or philosophy? It is a great choice if you want to create a key type as unions or enums. 589). I specialize in React, Node.js & TypeScript application development. when doing. Connect and share knowledge within a single location that is structured and easy to search. The Record type is a pre-defined TypeScript utility type and it has the following structure. I'd be thankful for any suggestion how to fix this? The following type P is the same type as type P = "x" | "y": If the type has a string or number index signature, keyof will return those types instead: Note that in this example, M is string | number this is because JavaScript object keys are . Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Typescript object: How do I restrict the keys to specific strings? Does Iowa have more farmland suitable for growing corn and wheat than Canada? With string enums this is easy because there is no reverse mapping from values to keys, so Object.keys(Colour).map(k => Colour[k as any]) is ['RED', 'GREEN']. Filter out the unnecessary values for numeric enums. What should I do? Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned. I don't remember the specific answer I gave to your other question, but not everything that works for classes will work the same way for enums :), @Tomas glad to help keep the interesting questions coming :), @Titan, I think your solution might be improved a bit by using indexing types like, How terrifying is giving a conference talk? I want to map to option tags for a select, i.e. 589). Helo Stack Community, By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. If you want all of your Enum values to be required do this: Or if you only want values in your enum but any amount of them you can add ? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. How terrifying is giving a conference talk? Is it legal to not accept cash as a brick and mortar establishment in France? export enum Colors { 'red', 'green', 'blue' } export type ColorInterface = Record<Colors, boolean> // translates to: export type ColorInterface = { 0: boolean; 1: boolean; 2: boolean; } Conclusions from title-drafting and question-content assistance experiments Use similar, derived property names in multiple Typescript interfaces or create new interfaces based on interface property names. My Question, is it not possible to have both these functinalities, Getting all values for the enum; Getting the string representation for label Defined in my QuestionType.ts file where the enum is define? Zerk caps for trailer bearings Installation, tools, and supplies. Why does this journey to the moon take so long? Typescript enum generic mapping The closest I could get is something like the following: This works for all enums (without custom initializers), but it would also accept other arrays as input (and then fail because the method body relies on the very specific key structure that TypeScript enums have). And if you do have this need (and this might very well be an X-Y-problem that can be solved in a better, completely different way given more context), use any, because you have left typesafe territory anyway. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, If you want to do it dynamically, taking only keys that are present in the. typescript - Using string enum as Map keys But Enums generate a lot of code, and by introducing the const keyword in TypeScript alongside our Enums, we can alleviate a lot of generated code. This should be the accepted answer. This is just the solution I was looking for. Asking for help, clarification, or responding to other answers. The bad thing is, that it is little code duplication. why not define a enum type in ts? Making statements based on opinion; back them up with references or personal experience. For now, to support my use case I just falled back to using primitives in my signature :(. Is iMac FusionDrive->dual SSD migration any different from HDD->SDD upgrade from Time Machine perspective? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned. Number indexers don't constrain non-number key types. As in, there should be exactly one value in the lookup for every key of the enum. You'd think this would be low-hanging fruit and yet we've resigned ourselves to using a ts-ignore. Asking for help, clarification, or responding to other answers. Or perhaps specify the type as the value? able to leverage the fact that it knows the exact set of values that I am Tim Mouskhelichvili, a Freelance Developer & Consultant from Montreal, Canada. How and when did the plasma get replaced with water? Adding labels on map layout legend boxes using QGIS. This data structure has many names: a map, a dictionary, an associative array Its functionality, however, always remains the same. This [x: number] property doesn't exist with a string enum. Typescript/Javascript: using tuple as key of Map Which field is more rigorous, mathematics or philosophy? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The EnumDictionary defined this way is basically the built in Record type: As of TypeScript 2.9, you can use the syntax { [P in K]: XXX }. Does Iowa have more farmland suitable for growing corn and wheat than Canada? The good thing is, that it's simple and you won't encounter unexpected behavior. Where to start with a large crack the lock puzzle like this? A Faster Approach to Enum Props in React - Jwstanly Distances of Fermat point from vertices of a triangle, A conditional block with unconditional intermediate code, Excel Needs Key For Microsoft 365 Family Subscription. union of each enum member. Another possible option not mentioned above is using the actual values. How would life, that thrives on the magic of trees, survive in an area with limited trees? The Overflow #186: Do large language models know what theyre talking about? like this: Given your use case I'm sharing a strategy I often use to solve this kind of problem although it's not strictly an Enum approach. Does TypeScript allow an enum to be assigned to an interface's object key? Why does tblr not work with commands that contain &? Id like to use a TypeScript enum with string values as Map key: This works fine. See the updated code sample, https://github.com/Microsoft/TypeScript/issues/17198, How terrifying is giving a conference talk? Code To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This answer might now in fact be outdated! We and our partners share information on your use of this website to help improve your experience. What is the motivation for infinity category theory? What's the significance of a C function declaration in parentheses apparently forever calling itself? How to use enum as index key type in typescript? What is Catholic Church position regarding alcohol? Adding labels on map layout legend boxes using QGIS, MSE of a regression obtianed from Least Squares. You are using depositTypes.enumKey which is looking for the literal key 'enumKey' rather than depositTypes[enumKey] which looks for the key of this current variable.