1var assert = require('assert');
2
3function missingNumbers(numArr) {
4  let missing = [];
5
6  for (let i = 1; i < numArr.length; i++) {
7    // check where there are gaps
8    if (numArr[i] - numArr[i - 1] != 1) {
9      let x = numArr[i] - numArr[i - 1];
10      let diff = 1;
11      while (diff < x) {
12        missing.push(numArr[i - 1] + diff);
13        diff++;
14      }
15    }
16  }
17
18  return missing;
19}
20
21try {
22  assert.deepEqual(missingNumbers([0, 1, 3]), [2]);
23
24  console.log('PASSED: ' + 'missingNumbers([0, 1, 3]) should equal [2]');
25} catch (err) {
26  console.log(err);
27}
28
29try {
30  assert.deepEqual(missingNumbers([10, 11, 14, 17]), [12, 13, 15, 16]);
31
32  console.log(
33    'PASSED: missingNumbers([10, 11, 14, 17]) should equal [ 12, 13, 15, 16 ]'
34  );
35} catch (err) {
36  console.log(err);
37}
38
39try {
40  assert.deepEqual(
41    missingNumbers([3, 7, 9, 19]),
42    [4, 5, 6, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18]
43  );
44
45  console.log(
46    'PASSED: missingNumbers([3, 7, 9, 19]) should equal [ 4, 5, 6, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18 ]'
47  );
48} catch (err) {
49  console.log(err);
50}