Getting the enum key with the value string (reverse mapping) in TypeScript Ask Question Asked 4 years, 5 months ago Modified 2 months ago Viewed 105k times 63 I have an enum: export enum ApiMessages { logged_ok = 'Logged OK', register_ok = 'Register OK' } I have a function with the enum as a parameter: You can either use bracket notation or a combination of Object.values and Object.keys. Find centralized, trusted content and collaborate around the technologies you use most. OpenAI chat functions on Android. enum FooKeys { FOO = 'foo', BAR = 'bar', } type FooValues =`$ {FooKeys}`; // this equals 'foo' | 'bar'. Access an enum by index in TypeScript Using the Object.values () method Using the Object.keys () method Summary Access an enum by index in TypeScript Enum is a kind of 'class' that allows us to create a group of constant values. Ask Question Asked 3 years, 3 months ago Modified 3 years, 3 months ago Viewed 242 times -3 I have this enum: export enum myEnum { name1 = 'my name', name2 = 'my other name', name3 = 'other' } and i have a myEnum object: const x = myEnum.name1; console.log (x) // prints 'my name' This is now available in TypeScript too. Normally, we will access an enum like this: The enum type does actually gets compiled into a JavaScript object enum-js-object.ts This program when compiled produces the following output. I'm new and learning typescript, currently - enums, and somehow this example throw me an error, i don't understand why. What are enums and types? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Conclusion. To convert string to Enum in Typescript or angular follow the below steps. The examples in the documentation all don't use the mapping enum TraitReportType { LAYOUT, EMBEDDED }. Here is an example of using bracket notation: enum Countries { Argentina = 'AR' as any, Armenia = 'AM' as any, Australia = 'AU' as any, Austria = 'AT' as any } console.log(Countries['AR']) Here's how you can do it: In the above code, we first define our enum MyEnum. Connect and share knowledge within a single location that is structured and easy to search. Even if the member type is known at compile time, the compiler currently does not provide a type mapping from an enum member to its respective enum type, as of TypeScript v4.8. Let's see several ways of creating enums type Simple Enum example enum WeekEnd { Sunday, Saturday } console.log (WeekEnd); // { '0': 'sunday', '1': 'saturday', sunday: 0, saturday: 1 } Probability of getting 2 cards with the same color. This post will walk through the code to implement a "chat function" in the JetchatAI sample app . so that don't have to write same method again on multiple places. To get the enum key by value in Typescript, you can use a reverse map. What you could do is implement an enum class, rather than using TypeScript's built-in enum. In TypeScript, enums, or enumerated types, are data structures of constant length that hold a set of constant values. When it comes specifically to TypeScript enums, it is not possible to know from what enum type a value came from. Thanks for contributing an answer to Stack Overflow! 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. Sorted by: 125. export enum QuestionType { PLAIN_TEXT = 0, SINGLE_SELECT_OPTION = 1, MULTI_SELECT_OPTION . How to get current date and time in typescript? head and tail light connected to a single battery? If one truly needs to point back to which enum it came from, then one either needs to encode that information alongside the enum value, or use classes instead of enums. To get an enum key by its value in Typescript using Object.keys () and Array.find (), you can follow these steps: Define your enum with key-value pairs: enum MyEnum { Key1 = "Value1", Key2 = "Value2", Key3 = "Value3", } Create a function that takes the enum value as an argument and returns the corresponding key: We then create a new object reverseMap with keys of type number and values of type string. Get Enum values as an Array in TypeScript Get all Enum Names as an Array in TypeScript Convert an Enum to an Array of Objects in TypeScript Get the length of an Enum in TypeScript If you need to get the length of an Enum, click on the following subheading: Get the length of an Enum in TypeScript # Get Enum values as an Array in TypeScript We can use this construct as shown in the example below: How can I manually (on paper) calculate a Bitcoin public key from a private key? TypeScript provides both numeric and string-based enums. I tried the following two methods: var enumVar: MyEnum = . We use Object.keys to loop through each key in the MyEnum object. There are three types of enums: enum SomeEnum { A, B } let enumValues:Array<string>= []; for (let value in SomeEnum) { if (typeof SomeEnum [value] === 'number') { enumValues.push (value); } } enumValues.forEach (v=> console.log (v)) //A //B Got any TypeScript Question? The TypeScript docs define enums as follows: Enums allow us to define a set of named constants. Were there any planes used in WWII that were able to shoot their own tail? They are just named values, unlike in Java where they are fully qualified objects with enum semantics. -1. Define a function that takes the enum value as an argument and returns its corresponding key: Call the function with the enum value and the enum object: Create a function that takes the enum value as an argument and returns the corresponding key: Use the function to get the key for a specific enum value. Note: There are some added benefits to this; for example, currently in TypeScript, you can't do T extends enum, but with this approach, you can do T extends Enum. 2.If the string is part of the enum name entry the value will be returned. Method 2: Using a loop and an if statement, Method 3: Using Object.keys() and Array.find(). When to use enums When to avoid enums Types of TypeScript enums Numeric enums Custom numeric enums Computed enums Const enums String enums Heterogeneous enums Using enums for reverse mapping Extracting object types of enums How to convert an enum to an array TypeScript enums vs. alternatives Using enums can make it easier to document intent, or create a set of distinct cases. Does Iowa have more farmland suitable for growing corn and wheat than Canada? How to get all enum values from a single enum value in typescript? At compile time, the enum itself is erased, and all that is left (for non-const) enums is a simple object; for example You'll notice there that the object itself, of course has a type (MyNumber), but the members of MyNumber are not of type MyNumber, and this is why you cannot identify the type of an enum from one of its members. The function then loops through the object keys and checks if the value of each key matches the given value. If a match is found, the function returns the key. QuestionType.ts. July 13th, 2023 0 0. In simple words, enums allow us to declare a set of named constants i.e. Enums Enums are one of the few features TypeScript has which is not a type-level extension of JavaScript. Following code can be used to create an enum in TypeScript: enum e { hello = 1, world = 2 }; And the values can be accessed by: e.hello; e.world; How do I create an enum with string va. Note: Enums in TypeScript (and even C#) suck! Ask any TypeScript Questions and Get Instant Answers from ChatGPT AI: ChatGPT answer me! Getting all values for the enum; Getting the string representation for label Defined in my QuestionType.ts file where the enum is define? Even if the member type is known at compile time, the compiler currently does not provide a type mapping from an enum member to its respective enum type, as of TypeScript v4.8. 4 Answers. Use the indexOf () method to get the index of the value in the array. Use the forEach () method to iterate over the array. 2021.02.16 2023.05.04 . Use the Object.keys () method to get an array of the enum's keys. How to set a variable if undefined in typescript? How to get enum key with enum value in typescript. This is more evident when understanding that a (non-const) enum compiles to an object which maps from keys to values and vice versa. Does ETB trigger after legendary rule resolution? To learn more, see our tips on writing great answers. What is the name of this plant and its fruits? Enums are a TypeScript-only feature, by which I mean, there is no formal definition of an enum in JavaScript. Note that this method assumes that each enum value is unique. 1st way: just simply turn off the type checking for the next line, which is similar to asserting the type of MyEnum to <any> as done in the @annepic 's answer. How to disable @typescript-eslint/no-non-null-assertion rule? TypeScript: How to get the keys of an enum as type? In this example, we set valueToFind to 2, which corresponds to the Second key in the MyEnum object. Enums allow you to define a set of values that are logically related to each other. 2. ; $http.put (url, { enumVar: <number>enumVar }); ( $http is AngularJS's HTTP service) Viewed 9 times. We looked at how to create JSON Schema from TypeScript types in this article. a collection of related values that can be numeric or string values. Making statements based on opinion; back them up with references or personal experience. Numeric enums If I'm only given a variable myVar, I know it's an enum value, but I don't know what the actual enum is. It creates using the enum keyword. Each of these constant values is known as a member of the enum. index.ts We then use the reverseMap object to find the key and log it to the console. Will spinning a bullet really fast without changing its linear velocity make it do more damage? In your fiddle, the function knows about MyNumber. index.ts Pros and cons of "anything-can-happen" UB versus allowing particular deviations from sequential progran execution, Condition for an equivalence of functor categories to imply an equivalence of categories. To get an enum key by value: Use the Object.values () method to get an array of the enum's values. Temporary policy: Generative AI (e.g., ChatGPT) is banned. Enums come in two flavors string and numeric. This involves creating a new object that maps the values to their corresponding keys. For each key, we get its value and use it to set the corresponding key in the reverseMap object. TypeScript provides both numeric and string-based enums. October 27, 2017 TypeScript 2.4 implemented one of the most requested features: string enums, or, to be more precise, enums with string-valued members. Why can't capacitors on PCBs be measured with a multimeter? TypeScript Enums Previous Next An enum is a special "class" that represents a group of constants (unchangeable variables). Why was there a second saw blade in the first grail challenge? As like mentioned in stackoverflow.com/questions/40227401/const-enum-in-typescript - Maniraj Murugan Jun 11, 2019 at 5:11 Add a comment 3 Answers Sorted by: 1 Your syntax is wrong. The given condition is that the actual enum MyNumber is unknown. - Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, Thanks for the fiddle, but that's not what I'm asking for. How terrifying is giving a conference talk? TypeScript 5.0 manages to make all enums into union enums by creating a . You should not assign it, or try to assign Enums as variables. Enum is a predefined constant in typescript. Getting an Enum element by it's value in TYPESCRIPT. Enums are useful when setting properties or values that can only be a certain number of possible values. Typescript enum get value by key and key by value. It is now possible to assign a string value to an enum member: enum MediaTypes { JSON = "application/json", XML = "application/xml", } The string enum can be used like any other enum in TypeScript: ; $http.put (url, { enumVar: enumVar }); This won't work also: var enumVar: MyEnum = . Have you tried removing the enum values or using "embedded" on the query side? How to get all Enum Flags from a Number in TypeScript? Is there a way to infer the enum type and get all possible enum values from this variable myVar? Before looking into the syntax of keyof enum, we need to know how keyof is used or its syntax, keyof sample_key sample_key = Type; So, here sample_key is the type for which keyof is being applied. but it looks like a hack and depends on the implementation of enum in TypeScript, which I'm not sure is guaranteed to stay the same. (@input property)? How to make bibliography to work in subfiles of a subfile? To get an enum key by its value in Typescript using Object.keys() and Array.find(), you can follow these steps: How to check if value is nan in typescript? Explains how to get value by key, get key by value, and use an enum as an object key. How to check if an object implements an interface in Typescript. To get the enum key by its value in TypeScript using a loop and an if statement, you can follow these steps: In this example, the getKeyByValue() function takes two arguments: the enum value you want to find the key for, and the enum object itself. Also easier to update at on place. 589). For Vanilla Js it should be like below: enum Colors { RED = "RED COLOR", BLUE = "BLUE COLOR", GREEN = "GREEN COLOR" } For .tsx it should be like below: However, keep in mind that it does require extra memory to store the reverse map object. // @ts-ignore MyEnum [x] 2nd: If u still want to keep the powerful typechecking feature of TS . . By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In your TS type, you are mapping to a lower case string. Just export enum ComplianceType will do. Here's an example of an enum in TypeScript: In TypeScript, enums allow you to define a set of named constants with a numeric value. Given an enumeration such as. 2021.07.08 2023.04.12. Why use enums? We can then reference keys using a public getter: private _supportedLanguages = Object.keys ( SupportedLanguages); public get supportedLanguages (): Array<string> { return this._supportedLanguages; } enums are not natively supported in JavaScript, but there is a workaround that lets us replicate their behavior in the language using the Object.freeze construct, since TypeScript treats enums as if they were real objects (although applicable for non-const enums at runtime ). type MyEnum = 'first' | 'second' | 'third'; The [number] tells Typescript to get all the "number based subscripts" of the array. How can it be "unfortunate" while this is what the experiments want? The enum's keys are all strings whereas its values are a mix of numbers and strings (the numbers being the actual enum values and the strings being its keys). We can guarantee that our data follows a rigorous schema and take advantage of TypeScript's static type-checking by utilizing TypeScript types to build JSON Schema. If one truly needs to point back to which enum it came from, then one either needs to encode that information alongside the enum value, or use classes instead of enums. Here's a code: enum IStatus { SUCCESS = 'success', FAILED = 'failed' } interface ResponseSuccess { databaseId: number sum: number from: number to: number } interface ResponseFail { errorMessage: string . 8 Answers Sorted by: 67 If you want to get your enum key by value in that case you have to rewrite your enum in following manners: But same format also might be work in older version as well. 1.Pass the given string to Enum object as a key. Stack Overflow at WeAreDevelopers World Congress in Berlin. For numbers: we can either create string union the same way or: starting TS 5.0. If multiple keys have the same value, this method will only return the first key it finds. The additional advantage, is, if you make changes to the VALID_ENUM_VALUES array, the MyEnum changes with it. For strings: you can create a string union from enum values using a template string. There are three basic types of enum: numeric, string, and heterogeneous. How to detect changes in an array? While it's possible to get the value of an enum member from its key, it's not as straightforward to get the key from its value. If you want to perform this reverse lookup in TypeScript, there are a few methods you can use. Denys Fisher, of Spirograph fame, using a computer late 1976, early 1977. Lets start with numeric. Is there a simple way to get a list of keys/numbers from enum in typescript? rev2023.7.17.43537. How to get enum key by value in Typescript? This is because the values of an enum are encoded underneath either as numbers or strings, and do not hold any references to their enum source. Enums allow a developer to define a set of named constants. type keyofEnum = keyof sample_keys; Syntax: Here is the syntax of keyof enum in TypeScript. 1 Did you try removing const from enum?? So, if you were to type the following code in the editor: You can assign values to Enum keys, one of the reasons why devs detest enums is the fact that typescript automatically assigns numerical values which is in fact not good for database' Enum, this is a non-issue because you can assign a string value to enums making them 13 Jul 2023 21:46:54 As we can see, we get the expected 200 status response, indicating a successful request. Thus, all we need to do to fetch an enum's keys is pass it to the static Object.keys () method. Typescript: How to get the enum "name" with its value? Some functions don't behave as expected when an enum has number values or mixed type data. Filter out any unnecessary values. 2 min # Iterate over Enums in TypeScript To iterate over enums: Use the Object.keys () or Object.values () methods to get an array of the enum's keys or values. Access the array of keys at the specific index. Enums or enumerations are a new data type supported in TypeScript. Hello prompt engineers, OpenAI recently announced a new feature - function calling - that makes it easier to extend the chat API with external data and functionality. Numeric Enums - Default By default, enums will initialize the first value to 0 and add 1 to each additional value: How would you get a medieval economy to accept fiat currency? How can I get the numeric value of the enum variable? Getting values from Typescript enum with strings. Let's look at this code below: Example: TypeScript 12 1 enum foodList { 2 Apples, 3 Avocados, 4 Bananas, 5 Blueberries, 6 Oranges, 7 Finally, we can use the reverseMap object to find the key for a given value. // define an enum["SLOW"] = 0] =. Get an enum key by value in TypeScript Use Object.keys () method Use square brackets Summary: Get an enum key by value in TypeScript To understand enums straightforwardly, let's dig deeper into how enums work. I've seen this practice used quite a lot in the C# community. (Ep. There are two ways to get enum keys by values in TypeScript. Asking for help, clarification, or responding to other answers. In TypeScript, an enum is a way to define a set of named constants.
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