typescript enums are bad

The short answer is probably, because TypeScript string enums should satisfy the majority of conventional use cases of idiomatic enums. readonly BANNED: "banned"; By understanding their benefits, limitations, and best practices, developers can leverage Enums effectively in their projects. Admittedly, it is just as safe and only marginally more verbose to use POJO enums which are unlikely to change in implementation as they are simply JS objects, and which provide the same benefits without having to concern developers with all the semantics of different enum variants. or if anywhere else in the code you typed the value you will be received at runtime as string and you want to pass it to a function which expects an enum, then just cast it. Enum member values can either be constant or computed, as we have earlier discussed. The rest (type space) communicates to TypeScript what that object represents at compile time. We're a place where coders share, stay up-to-date and grow their careers. Yes, Enums are compiled to something, while UnionTypes are simply stripped away, so your Javascript will be bigger. And we re-configured typegeneration to emit the unions for GQL enums. Ill point out where the trouble with enums can be particularly pervasive and fruit = Fruits[value as Fruits];. They are one of the few features of TypeScript which isn't a type-level extension of JavaScript. Reddit, Inc. 2023. In the following TypeScript Playground example, the --strict flag (and Lets say you have a service which returns a JSON payload when called and you want to model a property of that service as an enum value. And that's it -- everything works. Personally, I use Union Types when my String has 2 or max 3 values, as soon as the options become more, I switch to Enums. Embrace Enums wisely and harness their advantages to write cleaner and more maintainable code. The transpiled JS is intuitive and as expected, matching the output of the JS enum with const assertion like so: Additionally, we can be stricter about accessing enum members explicitly rather than with magic values like "apple", and throw type errors otherwise. Spends his time untangling software architectures and doing DevOps. following example used to accomplish that. The reason for this is that these constants are often easier to read than the value which the enum represents. In the case that printApple() is called multiple times in the codebase and we want to update the naming to be more specific or fix a typo, we will have to do this for each instance of the printApple() call. Enums are useful when setting properties or values that can only be a certain number of possible values. We're a place where coders share, stay up-to-date and grow their careers. This means that the first enum value variant is falsy, while every other value is truthy. The "hidden" truth is that TypeScript enums are transpiled to JavaScript objects in an unintuitive way. Specifying enum member values # TypeScript distinguishes three ways of specifying enum member values: Literal enum members are initialized: implicitly or; via number literals or string literals (explicitly). The result is not so satisfying than what we could expect as it's very verbose. Writing this code may make you think that youve uncovered a bug in the TypeScript type system but it turns out that this is intended behaviour for this type of enum. But theres another reason that this can be useful, and thats for using enums for bit flags. Made with love and Ruby on Rails. // <-- Triggering Intellisense here will display the available enum values (Info, Warning, Error). In addition to that, we can also do it on a subset of them: Here, weve specified that the value of 10 will represent Wednesday, but everything else will be left as is. So, therefore we can pass in numbers to a function that expects an enum, the enum itself is both a number and a defined constant. Optimize Enums in TypeScript with "const" - Ultimate Courses To summarize everything, the good things about enums are: They can be assigned either numeric or string values, and these values cannot be reassigned later in the code. Enum Serialization: Enums are serialized as their numeric value by default. Advisory boards arent just for executives. Google TypeScript Style Guide - GitHub Enumerations (or enums) are a supported data type in TypeScript. One reason to avoid using enums is the extra code they generate at compile time. In this article we'll see why it's so verbose and what other solutions can improve our code. In this article, we will show you why and how to avoid their use. If youre not, In strict mode, were forced to address this issue. For me StringEnums work perfectly, allow clean, readable, organised list of values and you can benefit from autocomplete features from your IDE, you have warnings at compile time if you use it wrong ( trying to pass around values that are not enums). However - it is interesting to see and understand the confusing drama behind enums. In java you can add getters to enums, private fields, constructors and assign tuple values to them. Given the following enum enum Verbosity { quiet = -1, normal = 0, verbose = 1, veryVerbose = 2, debug = 3, } How can I use greater than in a condition? } An enum easily thoughtbot, inc. Enums, short for "enumerations," are a type of data structure commonly found in programming languages. Just change the userStatus object values. DEV Community A constructive and inclusive social network for software developers. Sure, probably in plain JS I would have directly written: or even better ( if you really want to prevent your constants to be changed at runtime). Get ready to be surprised! In TypeScript, enums have a few surprising limitations. TypeScript enums are a fine tool for creating a set of related constants or options. Templates let you quickly answer FAQs or store snippets for re-use. While it be significantly bigger? Content is licensed under array: As opposed to enums, this has a few benefits: Enums can be challenging to use if you frequently need to check for existence of Or do we want to start wining and arguing that even bundled and minified code loaded in the browser is not readable? Your Color is a perfect fit for enums. One of the current trends in the TypeScript space seems to be criticising TypeScript native enums and claiming they are unsafe to use. If you haven't noticed, enums are objects, so you can iterate over an enum. Union types appear to offer a more concise, readable list of values than TypeScript enums do! So, on the application level we had to refactor our enums to the UNIONS. Nominal type systems consider each defined type to be unique, and thus even if types share the same data or value, they cannot be referenced equivalently. over enums in certain cases, especially if you want access to both the type and The constants-in-an-object approach interoperates with JavaScript with a minimum amount of friction. Here is what you can do to flag ishanbagchi: ishanbagchi consistently posts content that violates DEV Community's Enums are a new data type supported in TypeScript. There are two quick ways to get started with TS, suggested by its official website: via NPM Node.js package manager or by installing plugins for Visual Studio, a full-fledged IDE from Microsoft. How to create enum like type in TypeScript? - Stack Overflow As a result, its recommended that you dont use heterogeneous enums unless youre really sure its what you need. Lets take our FileState enum from above and add a new state for the file, ReadWrite: Then assuming we have a function that takes the enum we can write code such as this: Notice how were using the | operator on the FileState enum and this allows us to perform a bitwise operation on them to create a new enum value, in this case itll create 3, which is the value of the ReadWrite state. // Produces -> [(0, 1, 2, Apple, Banana, Mango)]; // Helper type to get a type for possible keys of enum, // No type errors, and does not demand FruitEnumPojo.APPLE, // (["APPLE", "apple"], ["BANANA", "banana"], ["MANGO", "mango"]), // Type error thrown! But I actually tried verifying this assumption yesterday in VS Code (my main IDE) and it actually works: put your cursor inside one of the union type members, initiate the rename command, change the value and see its usages updated elsewhere. It will become hidden in your post, but will still be visible via the comment's permalink. It will become hidden in your post, but will still be visible via the comment's permalink. INACTIVE: string; While Enums may not be suitable for every scenario, they provide a valuable option in the TypeScript toolkit. Well, TypeScript enums are actually just syntactic sugar for objects, under the hood they are just objects with keys and values. I feel envious of Rust enums, and I would love to have something similar in TypeScript. is it possible to write this without an enum? : r/typescript - Reddit Here's an example: enum Operators { Add, Subtract } function calculate(op: Operators, firstNumber: number, secondNumber: number) { switch(op) { case Operators.Add: return . \n Once unpublished, all posts by ishanbagchi will become hidden and only accessible to themselves. Enums. a string or numeric value within them. This is useful when the value is not important. 6 - Convert Typescript Enums to Array. ENUMs generate additional code at compile time, which increases the size of the final file. Well, we met the problems with enums when we started using automatic type generation from GraphQL-schema. However, it's worth noting that this solution may not be suitable for all use cases, especially when the number of values is very large. Enum, short for Enumerated Type, is a common language feature of many statically typed languages such as C, C#, Java, and Swift. Sunday or Monday? typescript - How to use greater than to compare enum values? - Stack TypeScript enums are a fine tool for creating a set of related constants or options. 1? Of course, the answer is yes. For example, if we wanted to model a list of fruits to use in a select For constant enums, the enum must be the first member and it has no initializer. Weve seen that an enum will have a numeric value assigned to it by default or we can explicitly do it on all of them, but we can also do it on a subset of them: Here weve specified that the value of 10 will represent Wednesday, but everything else will be left as is, so what does that generate in JavaScript? Enums are used in most object-oriented programming languages like Java and C# and are now available in TypeScript too. This is a rather strange statement considering that typescript always generates more code than you write. So why is it useful? Strings may cause problems by variations in spelling and capitalisation. Let's see this example: As you can see enums are a named type and only accept enum-specific values, not compatible or similar values, which can lead to compatibility issues and should be carefully considered when designing and using enums. Change the DB as you wish | Repository Pattern . Enums Can Become Bloated: Enums with a large number of values can become cumbersome to manage. typescript - Enum type not defined at runtime - Stack Overflow In particular, it can be challenging to check whether or not a value is in an enum in a type-safe way. Whatever output it gives by default is good enough to reduce the cognitive overload on the team. They allow developers to express intent and enforce type safety, preventing the use of invalid values. What weve done here is created a numeric enum, and if we look at the generated JavaScript it might be a bit clearer: Youll notice that the enum is really just a JavaScript object with properties under the hood. Enum is not defined. The ECMAScript Enums proposal doesn't seem to be going anywhere. 2. typescript does not recognize exported enum. You'll discover that there are much safer and reliable alternatives that you can use instead. We need it to be sure that we don't return an unexpected (undeclared) error code to clients and we correctly interpret the GQL-parameters received from the clients. If you disagree or have any further comments or questions, please dont hesitate to contact me directly - I would be very happy to change my mind and fill any personal knowledge gaps ! BANNED: string; And what is the first Entry? TypeScript's number enums behave in a few strange ways. Privacy Policy. TypeScript coerces the any silently. Metalhead Father of 2 Once unsuspended, dvddpl will be able to comment and publish posts again. A much safer alternative and guarantee of compatibility is the use of objects. So the object is the JavaScript (value space) part. However, there are potential pitfalls and limitations with const enum that should be considered. Union types, a.k.a. Afterwards, you can do cool stuff like pattern matching on the enum variants and extract the data from them. Rendering React Components: A Comparison of for Loops and .map(), GitHub Copilot Introduces Voice Coding: Enhancing Developer Productivity. But things may not always be as they seem, what do you think you get if you pass this through the TypeScript compiler? // Error: Type 'Month.Jan' is not assignable to type 'Month'. Initially, the values are defined using their position in the index with Sunday through Tuesday being 0 to 2. One way is by using POJOs (or plain old JavaScript objects), which, as the name suggests, uses a simple JavaScript object in place of a TypeScript enum which will look like this: As seen, there are no tricks employed here, this is a plain and simple JavaScript object, with an as const TypeScript assertion that enforces the object contents as read-only. In the above snippet, the union type requires the literal "APPLE" to be passed, so the code will be harder to refactor just as in the case of the POJO enum. It is recommended to use Enums for a small, well-defined set of related constants. keyof typof userStatus extracts the object property keys as a union (keyof type operator). Hopefully youre using TypeScript with the --strict flag. Problem 1: Iteration over Typescript enums requires converting to Array This might seem like a nitpick since ES6 gave us Object.values but if we consider the most common use cases for enums . The "enums as configuration" anti-pattern. This article will explore the potential problems with enums and suggest safer and more reliable alternatives. infer the same type if we use the Array.find method to resolve a value from One of the current trends in the TypeScript space seems to be criticising TypeScript native enums and claiming they are unsafe to use. OK, so string enums are great - but what about union types? widened to, Our array of values can never be modified. At first glance, enums are great - they allow you to store a set of read-only values in a concise, typesafe manner. However, there have been debates about whether TypeScript Enums are good or bad. As discussed, union types may pose an advantage over string enums if the following is true: In such a case, union types can offer a more concise and readable implementation of the enum idiom. TypeScript Enums, when used appropriately, can be a powerful tool for enhancing code readability, maintainability, and type safety. But there is also this unpleasant ambiguity. will not compile: view this example on typescript playground. easier to access the enum values. This is not clickbait. 1. Typescript have another interesting feature which are Union Types. 7 - Check if Value Exists in Typescript Enum. TypeScript Enums Previous Next An enum is a special "class" that represents a group of constants (unchangeable variables). Writer, Speaker, FOSS Maintainer Author While it's true that this detail is fixed if you use a constant enum, but I've been on multiple projects and seen people using regular enums everywhere and wonder why their output is so big. There is the notion of type declaration space and variable declaration space: The unfortunate thing is that TypeScript source code conflates both type and value space. Postada: I have been one of those people. But theres one special type that we want to discuss today and that is enums. TypeScript Enums are Terrible. Here's Why. : r/typescript - Reddit It is now read-only by definition. Personally I find that section very confusing. With you every step of your journey. This opens us up to a runtime error Unflagging ivanzm123 will restore default visibility to their posts. TypeScript string enums, and when and how to use them Disclaimer: this blog post was originally written for LogRocket. FIRST = 'name' However, we also cant pass in an arbitrary string, since the enum knows what string values are valid. If you have read the previous section, you can compare and manipulate enum variant values, so you can write something like: In the if statement above, we are comparing an enum value with a string. Which is still quite bad. thank you so much for sharing such an interesting insight! born GDR/Europe, Nx Champion Angular Hero of Education, B.Sc. If ivanzm123 is not suspended, they can still re-publish their posts from their dashboard. This is a recipe for disaster. -1. 3 - Typescript Enum Members as Types. In fact, we can mix and match the values of enums within an enum itself: Provided that all assignable values are of the same type (numeric in this case,) we can generate those numbers in a bunch of different ways, including computed values. By default, enums will initialize the first value to 0 and add 1 to each additional value: The key difference between union types and enums (apart from their syntax), is that union types are purely compile time concepts, whereas enums emit JavaScript objects that will exist at runtime. Enum variant values can be compared and manipulated, allowing for the creation of conditional statements based on them. Put the TypeScript enums and Booleans away - LogRocket Blog It has the named properties we defined, and they are assigned a number representing the position in the enum that they exist (Sunday being 0, Saturday being 6), but the object also has number keys with a string value representing the named constant. This is a false argument for typescript in general, let alone Enums. Syntax: Following is the syntax that we could use to initialize an enum in TypeScript- enum enum_name { // values.. } Enum vs. Union Types: In some scenarios, Union Types might be a better choice than Enums. Therefore, we can pass in numbers to a function that expects an enum. Have you ever wondered why TypeScript experts recommend avoiding the use of ENUMs?

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