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How do you assign default values while destructuring? How does the rest parameter differ from the spread operator, even though they use the same '...' syntax? How do you use spread to shallow-copy and merge objects? How do you destructure nested objects and arrays in one statement? How can you use destructuring to swap two variables without a temporary variable? How do computed property names interact with object destructuring?
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JavaScript › Destructuring, Spread & Rest

Why must the rest element be the LAST element in a destructuring pattern?

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Answer

Rest collects 'everything remaining' after the named elements are extracted, so its position only makes sense as the final element — putting it earlier would make the remaining count ambiguous, and JavaScript throws a SyntaxError.
const [first, ...rest] = [1, 2, 3, 4]; // valid: rest = [2,3,4]
// const [...rest, last] = [1,2,3]; // SyntaxError
Real-world example Splitting an array into its head and tail for recursive-style processing.

Common follow-ups: Does the same last-position rule apply to object rest destructuring?

Error Handling
All 10 Destructuring, Spread & Rest questions