Check if value exists in enum in TypeScript

Question

I recieve a number type   3 and have to check if it exists in this enum   export const MESSAGE TYPE         INFO  1      SUCCESS  2      WARNING  3      ERROR  4       The best way I found is by getting all Enum Values as an array and using indexOf on it  But the resulting code isn t very legible   if  -1  lt    values  MESSAGE TYPE   indexOf    toInteger  type                do stuff         Is there a simpler way of doing this

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export enum UserLevel     Staff   0    Leader    Manager     export enum Gender     None    none     Male    male     Female    female       Difference result in log   log Object keys Gender     gt     None    Male    Female     log Object keys UserLevel     gt     0    1    2    Staff    Leader    Manager      The solution  we need to remove key as a number    export class Util     static existValueInEnum type  any  value  any   boolean       return Object keys type  filter k   gt  isNaN Number k    filter k   gt  type k      value  length  gt  0          Usage     For string value if   Util existValueInEnum Gender   XYZ          todo      For number value  remember cast to Number using Number val  if   Util existValueInEnum UserLevel  0         todo

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If you want this to work with string enums  you need to use Object values ENUM  includes ENUM value  because string enums are not reverse mapped  according to https   www typescriptlang org docs handbook release-notes typescript-2-4 html   Enum Vehicle       Car    car       Bike    bike       Truck    truck      becomes         Car   car       Bike   bike       Truck   truck      So you just need to do   if  Object values Vehicle  includes  car             Do stuff here     If you get an error for  Property  values  does not exist on type  ObjectConstructor   then you are not targeting ES2017  You can either use this tsconfig json config    compilerOptions          lib     es2017       Or you can just do an any cast   if    lt any gt Object  values Vehicle  includes  car             Do stuff here

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If you want to use the variable as enum  just add the function  Enum EVehicle       Car    car       Bike    bike       Truck    truck     const getVehicleAsEnum    vehicleStr string    gt  vehicleStr      car    EVehicle Car   vehicleStr      bike    EVehicle Bike   vehicleStr      truck    EVehicle Truck   undefined  And then test  const vehicleEnum   getVecicleAsEnum str  if vehicleEnum          do something

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For anyone who comes here looking to validate if a string is one of the values of an enum and type convert it  I wrote this function that returns the proper type and returns undefined if the string is not in the enum  function keepIfInEnum lt T gt     value  string    enumObject     key  string   T         if  Object values enumObject  includes  value as unknown  as T         return  value as unknown  as T      else       return undefined         As an example  enum StringEnum     value1    FirstValue     value2    SecondValue     keepIfInEnum lt StringEnum gt   FirstValue   StringEnum       FirstValue  keepIfInEnum lt StringEnum gt   OtherValue   StringEnum      undefined

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There is a very simple and easy solution to your question   var districtId   210   if  DistrictsEnum districtId     null        Returns  undefined  if the districtId not exists in the DistrictsEnum      model handlingDistrictId   districtId

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enum ServicePlatform       UPLAY    quot uplay quot       PSN    quot psn quot       XBL    quot xbl quot     becomes    UPLAY   uplay   PSN   psn   XBL   xbl     so ServicePlatform UPLAY in ServicePlatform    false  SOLUTION  ServicePlatform UPLAY toUpperCase   in ServicePlatform    true

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This works only on non-const  number-based enums  For const enums or enums of other types  see this answer above  If you are using TypeScript  you can use an actual enum  Then you can check it using in  export enum MESSAGE TYPE       INFO   1      SUCCESS   2      WARNING   3      ERROR   4      var type   3   if  type in MESSAGE TYPE        This works because when you compile the above enum  it generates the below object         1    INFO        2    SUCCESS        3    WARNING        4    ERROR       INFO  1      SUCCESS  2      WARNING  3      ERROR  4

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Type assertion is un-avoidable  Following up on enum Vehicle       Car    car       Bike    bike       Truck    truck     I found one alternative that wasn t mentioned so thought I d share my fix for it  const someString  Vehicle   string    car   const inEnum    Object values Vehicle  as string    includes someString    I find this more truthful because we usually come in typesafe with a string  and want to compare it to the enum  it d be a bit reckless to typecast it to any reason  never do this  or Vehicle reason  likely untruthful   Instead  typecasting the Object values   output to an array of strings is in-fact very much real

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TypeScript v3 7 3   export enum YourEnum      enum1    enum1      enum2    enum2      enum3    enum3      const status    enumnumnum    if    status in YourEnum          throw new UnprocessableEntityResponse  Invalid enum val

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Update  I ve found that whenever I need to check if a value exists in an enum  I don t really need an enum and that a type is a better solution  So my enum in my original answer becomes  export type ValidColors        quot red quot       quot orange quot       quot yellow quot       quot green quot       quot blue quot       quot purple quot    Original answer  For clarity  I like to break the values and includes calls onto separate lines  Here s an example  export enum ValidColors     Red    quot red quot     Orange    quot orange quot     Yellow    quot yellow quot     Green    quot green quot     Blue    quot blue quot     Purple    quot purple quot      function isValidColor color  string   boolean     const options  string     Object values ButtonColors     return options includes color

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According to sandersn the best way to do this would be  Object values MESSAGE TYPE  includes type as MESSAGE TYPE

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