Spread Operator with Arrays

JavaScript's spread operator (...) is a powerful feature that works seamlessly with TypeScript's typed arrays. When you use the spread syntax to combine arrays, TypeScript automatically infers the correct type for the resulting array, maintaining full type safety throughout the operation.

The spread operator allows you to "spread out" the elements of an array into individual elements. When combining typed arrays, you simply use the spread syntax inside square brackets to create a new array:

let firstNumbers: number[] = [1, 2, 3];
let secondNumbers: number[] = [4, 5, 6];
let combined: number[] = [...firstNumbers, ...secondNumbers];
// Result: [1, 2, 3, 4, 5, 6]

TypeScript is smart enough to understand that when you spread two number[] arrays together, the result is also a number[]. This type inference works with any array type, whether it's strings, booleans, or custom objects.

You can even mix the spread operator with individual elements:

let scores: number[] = [85, 92];
let allScores: number[] = [100, ...scores, 78];
// Result: [100, 85, 92, 78]

This approach creates a new array without modifying the original arrays, which is particularly useful when working with immutable data patterns. The spread operator provides a clean, readable way to combine arrays while preserving TypeScript's type checking benefits.