Good morning! Here's our prompt for today.

Given an array, return another array with just the ordered unique elements from the given array. In other words, you're removing any duplicates.

Note: Order needs to be preserved, so no sorting should be done. And the order should be maintained with the first occurrence of the element in the given array.

1function uniques(arr) {
2  // fill in
3}
4
5let arr = [3, 5, 6, 9, 9, 4, 3, 12]
6uniques(arr);
7// Correct: [3, 5, 6, 9, 4, 12]
8// But this is incorrect: [5, 6, 9, 4, 3, 12]
9
10arr = [13, 5, 3, 5, 8, 13, 14, 5, 9]
11uniques(arr);
12// Correct: [13, 5, 3, 8, 14, 9]
13// Incorrect: [3, 5, 8, 13, 14, 9]

Constraints

• Length of the array <= 100000
• The values in the array between -1000000000 and 1000000000
• Expected time complexity: O(n)
• Expected space complexity: O(n)

Try to solve this here or in Interactive Mode.

How do I practice this challenge?

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var assert = require('assert');

​

function uniques(array) {

  // Fill in this method

  return array;

}

​

console.log(uniques([3, 5, 6, 9, 9, 4, 3, 12]));

​

try {

  assert.deepEqual(

    uniques([8, 8, 15, 6, 19, 7, 12, 6, 6, 3, 13, 9, 15, 14, 1, 13, 4, 11, 16]),

    [8, 15, 6, 19, 7, 12, 3, 13, 9, 14, 1, 4, 11, 16]

  );

​

  console.log(

    'PASSED: uniques([8,8,15,6,19,7,12,6,6,3,13,9,15,14,1,13,4,11,16]) should return [8,15,6,19,7,12,3,13,9,14,1,4,11,16]'

  );

} catch (err) {

  console.log(err);

}

​

try {

  assert.deepEqual(

    uniques([12, 7, 2, 20, 20, 2, 15, 20, 2, 10, 12, 1]),

    [12, 7, 2, 20, 15, 10, 1]

  );

​

  console.log(

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Here's our guided, illustrated walk-through.

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