Typescript Check If Value Is In Enum Top 13 Posts With The Most Views

To check if a value is in an enum in TypeScript, you can use the in operator or the hasOwnProperty method. Here’s an example:

typescript
enum Fruit {
  Apple = "apple",
  Banana = "banana",
  Orange = "orange"
}

const myFruit = "banana";

if (myFruit in Fruit) {
  console.log(`${myFruit} is a valid fruit in the Fruit enum`);
}

if (Fruit.hasOwnProperty(myFruit)) {
  console.log(`${myFruit} is a valid fruit in the Fruit enum`);
}

In this example, we define an enum Fruit with three values. We then define a variable myFruit with the value "banana". We use the in operator to check if myFruit is a valid value in the Fruit enum. Alternatively, we use the hasOwnProperty method to check if the Fruit enum has a property with the value of myFruit. If either check is true, we log a message to the console indicating that myFruit is a valid fruit in the Fruit enum.

To check the value of an enum in TypeScript, you can compare it to a specific enum member using the identity operator ===. For example, let’s say you have the following enum:

typescript
enum Direction {
  Up,
  Down,
  Left,
  Right,
}

You can check if a variable direction has the value Direction.Up like this:

typescript
const direction = Direction.Up;

if (direction === Direction.Up) {
  console.log("Direction is up!");
} else {
  console.log("Direction is not up.");
}

This will output “Direction is up!” because the direction variable has the value Direction.Up.

Alternatively, you can also use the switch statement to check for the value of an enum member like this:

typescript
const direction = Direction.Down;

switch (direction) {
  case Direction.Up:
    console.log("Direction is up!");
    break;
  case Direction.Down:
    console.log("Direction is down!");
    break;
  case Direction.Left:
    console.log("Direction is left!");
    break;
  case Direction.Right:
    console.log("Direction is right!");
    break;
  default:
    console.log("Unknown direction!");
    break;
}

This will output “Direction is down!” because the direction variable has the value Direction.Down.

To check if a value is defined in an enum in C#, you can use the Enum.IsDefined method. Here is an example:

csharp
enum DaysOfWeek {
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday,
    Sunday
}

bool isDefined = Enum.IsDefined(typeof(DaysOfWeek), "Monday");
Console.WriteLine(isDefined); // output: True

isDefined = Enum.IsDefined(typeof(DaysOfWeek), "InvalidValue");
Console.WriteLine(isDefined); // output: False

In this example, we define an enum called DaysOfWeek and then use the Enum.IsDefined method to check if the value "Monday" is defined in the enum. The IsDefined method returns true if the value is defined in the enum, and false otherwise. We then test the method with an invalid value, which returns false.

Note that the second argument of the Enum.IsDefined method is a string representing the name of the value you want to check, not the actual value itself. If you want to check if a particular integer value is defined in the enum, you can cast the integer value to the enum type before passing it to the IsDefined method.