JavaScript code assessment

JavaScriptIntermediate

submitted-code

function findFirstDuplicate(numbers) {
  const seen = new Set();
  for (const number of numbers) {
    if (seen.has(number)) return number;
    seen.add(number);
  }
  return null;
}

console.log(findFirstDuplicate([4, 7, 2, 7, 9]));

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✓

Stage 1Code review

Stage 2Understanding

Stage 3Debug challenge

Deterministic questionFunction contract

What is the job of `findFirstDuplicate`?

Describe the responsibility, inputs, output, and side effects of `findFirstDuplicate`.

Code focusLine 1

function findFirstDuplicate(numbers) {

Your answer