Question

113

How can I cast a string to an enum in Typescript

rated 0 times [ 120] [ 7] / answers: 1 / hits: 27803 / 4 Years ago, thu, july 9, 2020, 12:00:00

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

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kalynnkathrynd

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1 Year ago

answered 4 Years ago josefn · Accepted Answer

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...