How to create enum like type in TypeScript

Question

I m working on a definitions file for the Google maps API for TypeScript   And I need to define an enum like type eg  google maps Animation which contains two properties  BOUNCE and DROP   How should this be done in TypeScript

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As of TypeScript 0 9  currently an alpha release  you can use the enum definition like this   enum TShirtSize      Small     Medium     Large    var mySize   TShirtSize Large    By default  these enumerations will be assigned 0  1 and 2 respectively  If you want to explicitly set these numbers  you can do so as part of the enum declaration   Listing 6 2 Enumerations with explicit members  enum TShirtSize      Small   3     Medium   5     Large   8    var mySize   TShirtSize Large    Both of these examples lifted directly out of TypeScript for JavaScript Programmers   Note that this is different to the 0 8 specification  The 0 8 specification looked like this - but it was marked as experimental and likely to change  so you ll have to update any old code   Disclaimer - this 0 8 example would be broken in newer versions of the TypeScript compiler   enum TShirtSize     Small  3    Medium  5    Large  8    var mySize   TShirtSize Large

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TypeScript 0 9  has a specification for enums   enum AnimationType       BOUNCE      DROP      The final comma is optional

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Update   As noted by  iX3  Typescript 2 4 has support for enum strings    See Create an enum with string values in Typescript    Original answer   For String member values  TypeScript only allows numbers as enum member values  But there are a few solutions hacks you can implement   Solution 1   copied from  https   blog rsuter com how-to-implement-an-enum-with-string-values-in-typescript   There is a simple solution  Just cast the string literal to any before assigning   export enum Language       English    lt any gt  English       German    lt any gt  German       French    lt any gt  French       Italian    lt any gt  Italian      solution 2   copied from  https   basarat gitbooks io typescript content docs types literal-types html  You can use a string literal as a type  For example   let foo   Hello     Here we have created a variable called foo that will only allow the literal value  Hello  to be assigned to it  This is demonstrated below   let foo   Hello   foo    Bar      Error   Bar  is not assignable to type  Hello    They are not very useful on their own but can be combined in a type union to create a powerful  and useful  abstraction e g    type CardinalDirection        North         East         South         West    function move distance  number  direction  CardinalDirection                  move 1  North       Okay move 1  Nurth       Error

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This is now part of the language  See TypeScriptLang org   Basic Types   enum for the documentation on this  An excerpt from the documentation on how to use these enums   enum Color  Red  Green  Blue   var c  Color   Color Green    Or with manual backing numbers   enum Color  Red   1  Green   2  Blue   4   var c  Color   Color Green    You can also go back to the enum name by using for example Color 2    Here s an example of how this all goes together   module myModule       export enum Color  Red  Green  Blue        export class MyClass           myColor  Color           constructor                 console log this myColor               this myColor   Color Blue              console log this myColor               console log Color this myColor                       var foo   new myModule MyClass      This will log      undefined   2   Blue    Because  at the time of writing this  the Typescript Playground will generate this code     var myModule   function  myModule         function  Color            Color Color  Red     0     Red           Color Color  Green     1     Green           Color Color  Blue     2     Blue          myModule Color     myModule Color             var Color   myModule Color            var MyClass    function              function MyClass                 console log this myColor               this myColor   Color Blue              console log this myColor               console log Color this myColor                      return MyClass                myModule MyClass   MyClass     myModule     myModule         var foo   new myModule MyClass

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Enums in typescript   Enums are put into the typescript language to define a set of named constants  Using enums can make our life easier  The reason for this is that these constants are often easier to read than the value which the enum represents    Creating a enum   enum Direction       Up   1      Down      Left      Right      This example from the typescript docs explains very nicely how enums work  Notice that our first enum value  Up  is initialized with 1  All the following members of the number enum  are then auto incremented from this value  i e  Down   2  Left   3  Right   4   If we didn t initialize the first value with 1 the enum would start at 0 and then auto increment  i e  Down   1  Left   2  Right   3    Using an enum   We can access the values of the enum in the following manner   Direction Up         first the enum name  then the dot operator followed by the enum value Direction Down    Notice that this way we are much more descriptive in the way we write our code  Enums basically prevent us from using magic numbers  numbers which represent some entity because the programmer has given a meaning to them in a certain context   Magic numbers are bad because of the following reasons    We need to think harder  we first need to translate the number to an entity before we can reason about our code  If we review our code after a long while  or other programmers review our code  they don t necessarily know what is meant with these numbers

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Just another note that you can a id string enum with the following    class EnumyObjects      public static BOUNCE  str  Bounce  id 1       public static DROP  str  Drop  id 2       public static FALL  str  Fall  id 3

[enums] How to create enum like type in TypeScript?

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