CODEWITHSUNDEEP
javascriptnode.jstypescripttypescript-typings
Dylan Kerler
Dylan Kerler

Reputation: 2187

How can I cast a string to an enum in Typescript

Enum definition:

enum Colors {
  Red = "red",
  Blue = "blue"
}

How can I cast some arbitrary sting (e.g. a result from a GET request) to the enum?

const color: Colors = "blue"; // Gives an error

In addition, why do integer enums work but string enums fail to have the same behavior?

enum Colors {
  Red = 1,
  Blue
}

const color: Colors = 1; // Works

Upvotes: 26

Views: 42461

Answers (1)

JCOC611
JCOC611

Reputation: 19729

If you are sure that the strings will always correspond to an item in the enum, it should be alright to cast it:

enum Colors {
  Red = "red",
  Blue = "blue",
}

const color: Colors = <Colors> "blue";

It won't catch the cases where the string is not valid. You would have to do the check at runtime:

let colorName: string = "blue"; // from somewhere else
let color: Colors;
if (Object.values(Colors).some((col: string) => col === colorName))
  color = <Colors> colorName;
else
  // throw Exception or set default...

Upvotes: 37

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