Destructuring: position, skip, default, rest
The default only replaces undefined, so null stays null.
Array destructuring unpacks items into variables by position (const [a, b] = arr), with skipping, defaults and a ...rest to collect the remainder; spread (...arr) does the opposite, unpacking an array into a new array or a function call, which is how you copy and merge arrays.
Change the code and press Run (Ctrl+Enter). Predict what will happen first, then break it on purpose and read what changes. Your edits are saved and match the lesson page.
Ready for more? This phase has 6 hands-on exercises with automatic checks.
Practice questions
Write the code in the editor, run it, then open the model answer to compare.
Given const scores = [88, 72, 95, 60];, put the first score in top and the rest in others, and print both.
Write addToFront(arr, item) that returns a new array with item first, without changing arr.
Use destructuring to get the hours and minutes as numbers from the string "09:45".
Explain it without notes
How does array destructuring work, and what happens to missing items?
How do you swap two variables in JavaScript without a temporary variable?
What is the difference between rest and spread?
How do you merge two arrays and remove duplicates?
Console
(nothing was printed)Expected console output
10 20
10 30
0
10 [ 20, 30 ]
1 undefined
null