Literal Types
Literal types in TypeScript allow you to specify that a variable can only have one or more exact values, rather than any value of a broader type like string or number. This restriction helps prevent errors by ensuring that only expected values are used in your code.
1234567891011// String literal type let direction: "left" | "right" | "up" | "down"; direction = "left"; // OK direction = "up"; // OK // direction = "forward"; // Error: Type '"forward"' is not assignable to type '"left" | "right" | "up" | "down"' // Number literal type let diceRoll: 1 | 2 | 3 | 4 | 5 | 6; diceRoll = 4; // OK diceRoll = 6; // OK // diceRoll = 7; // Error: Type '7' is not assignable to type '1 | 2 | 3 | 4 | 5 | 6'
In the example above, the direction variable is limited to four possible string values: "left", "right", "up", or "down". Any attempt to assign a different string will result in a type error. Similarly, the diceRoll variable can only be one of the numbers from 1 to 6, matching the faces of a standard die. Literal types are especially useful for function parameters, configuration options, or any situation where only a specific set of values makes sense. By using literal types, you make your code safer, clearer, and more predictable.
Дякуємо за ваш відгук!
Запитати АІ
Запитати АІ
Запитайте про що завгодно або спробуйте одне із запропонованих запитань, щоб почати наш чат
Can you explain how to use literal types with function parameters?
What are some real-world use cases for literal types in TypeScript?
How do literal types differ from enums in TypeScript?
Awesome!
Completion rate improved to 8.33Literal Types
Свайпніть щоб показати меню
Literal types in TypeScript allow you to specify that a variable can only have one or more exact values, rather than any value of a broader type like string or number. This restriction helps prevent errors by ensuring that only expected values are used in your code.
1234567891011// String literal type let direction: "left" | "right" | "up" | "down"; direction = "left"; // OK direction = "up"; // OK // direction = "forward"; // Error: Type '"forward"' is not assignable to type '"left" | "right" | "up" | "down"' // Number literal type let diceRoll: 1 | 2 | 3 | 4 | 5 | 6; diceRoll = 4; // OK diceRoll = 6; // OK // diceRoll = 7; // Error: Type '7' is not assignable to type '1 | 2 | 3 | 4 | 5 | 6'
In the example above, the direction variable is limited to four possible string values: "left", "right", "up", or "down". Any attempt to assign a different string will result in a type error. Similarly, the diceRoll variable can only be one of the numbers from 1 to 6, matching the faces of a standard die. Literal types are especially useful for function parameters, configuration options, or any situation where only a specific set of values makes sense. By using literal types, you make your code safer, clearer, and more predictable.
Дякуємо за ваш відгук!
