8. Tuple

A tuple allows you to store a fixed number of elements with different types in a specific order.

Example:

// Declare a tuple type
let x: [string, number];
 
// Initialize it correctly
x = ["hello", 10]; // OK
 
// Initialize it incorrectly
x = [10, "hello"]; // Error: Type 'number' is not assignable to type 'string' and vice versa

Key Points:

1. Fixed Types: Each element in a tuple has a specific type in the order you define. The first element is expected to be a string, and the second a number.

   • x = ["hello", 10]; is valid because the types match.
   • x = [10, "hello"]; is invalid because the types are swapped.

2. Accessing Elements: You can access elements by index:

   console.log(x[0].substring(1));  // OK, string method on a string
   console.log(x[1].substring(1));  // Error, number doesn't have 'substring'

3. Length is Fixed: Tuples have a fixed length and type structure.

   • Attempting to assign values to indices outside the defined range will result in an error.

   x[3] = "world";  // Error: Property '3' does not exist on type '[string, number]'
   console.log(x[5].toString());  // Error: Property '5' does not exist on type '[string, number]'