Converting a String to Enum

In TypeScript, you can convert a string to an enum value by using the enum and valueOf() method. Enumerations, or enums, provide a way to define a set of named constants representing discrete values.

#1. Define an Enum

First, you need to define an enum that represents the possible string values.

enum Color {
  Red = "RED",
  Green = "GREEN",
  Blue = "BLUE",
}

In this example, we define an enum called Color with three constant values: "RED", "GREEN", and "BLUE".

#2. Convert a String to Enum

To convert a string to an enum value, you can use the valueOf() method.

function convertToColorEnum(str: string): Color | undefined {
  const colorValue = Color[str as keyof typeof Color];
  return colorValue;
}

const myColor = convertToColorEnum("GREEN");

if (myColor !== undefined) {
  console.log(myColor); // Output: Color.Green
} else {
  console.log("Invalid color string.");
}

In this example, we create a function convertToColorEnum() that takes a string parameter str. We use str as a key to access the enum value using the Color enum as the type. The valueOf() method converts the string to the corresponding enum value.

#3. Handling Invalid Strings

It is essential to handle scenarios where the input string does not match any enum value.

function convertToColorEnum(str: string): Color | undefined {
  const colorValue = Color[str as keyof typeof Color];
  return colorValue;
}

const myColor = convertToColorEnum("YELLOW");

if (myColor !== undefined) {
  console.log(myColor); // Output: Color.Yellow
} else {
  console.log("Invalid color string."); // Output: Invalid color string.
}

In this example, the string "YELLOW" does not match any enum value, so the function returns undefined, and the appropriate error message is displayed.