Once Guard

A Closer Look at Functionsmedium

Course · Section 10: A Closer Look at Functions · Lecture 144: Closures

Implement `onceResults(values)` that wraps a function so it returns its argument on the first call and `null` afterwards, applying it to each value and returning the results.

Sample tests

Input: onceResults([1,2,3])

Output: [1,null,null]

Input: onceResults([5])

Output: [5]

+ 1 hidden test run on Submit.

Hints

Common pitfalls

Forgetting to set the flag, so it never stops returning the value.

Learning resources

MDN: Closures

Approach & explanation (try first)

A captured boolean lets the wrapper return its argument on the first call and null on every later one.

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Run your code to see results.

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