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BasicJavaScript~5 min

Remove duplicates while keeping order

Warm-up question in JavaScript automation interviews

Points available

100/100

Your mission

  1. Read
  2. 2Run
  3. 3Submit
  4. 4Solve

Write unique(arr) that returns a new array without duplicates, keeping first occurrences in order.

Examples

unique([3, 1, 3, 2, 1]) → [3, 1, 2]

Hints

Each hint costs 10 points on a full solve.

Interviewer follow-ups

  • How would you de-duplicate an array of objects by `id`?

Ctrl+Enter to run · add Shift to submit

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Tab inserts two spaces. Press Escape, then Tab, to leave the editor.
Terminal

$ node solution.js

Run executes the open file. Submit scores solution.js against hidden tests.

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