test-repo/changelog_unreleased/javascript/10106.md

#### Concise formatting of number-only arrays (#10106, #10160 by @thorn0)

While in general, Prettier avoids this kind of formatting because it's not diff-friendly, in this special case we decided that the benefits outweigh the risks.

If at least one element has a trailing single-line (`// ...`) comment on the same line, the concise formatting isn't applied. On the other hand, single-line comments placed on separate lines don't have such an effect and – as well as empty lines – can be used for logical grouping.

<!-- prettier-ignore -->
```jsx
// Input
const lazyCatererNumbers  =  [1, 2, 4, 7, 11, 16, 22, 29, 37, 46,

// n > 10
56, 67, 79, 92, 106, 121, 137, 154, 172, 191, 211, 232, 254, 277, 301, 326, 352, 379, 407, 436, 466,
497, 529, 562, 596, 631, 667, 704, 742, 781,
// n > 40
821, 862, 904, 947, 991, 1036, 1082, 1129, 1177, 1226, 1276, 1327, 1379];

// Prettier stable
const lazyCatererNumbers = [
  1,
  2,
  4,
  7,
  11,
  16,
  22,
  29,
  37,
  // ... ✂ 46 lines ✂ ...
  1379,
];

// Prettier main
const lazyCatererNumbers = [
  1, 2, 4, 7, 11, 16, 22, 29, 37, 46,

  // n > 10
  56, 67, 79, 92, 106, 121, 137, 154, 172, 191, 211, 232, 254, 277, 301, 326,
  352, 379, 407, 436, 466, 497, 529, 562, 596, 631, 667, 704, 742, 781,
  // n > 40
  821, 862, 904, 947, 991, 1036, 1082, 1129, 1177, 1226, 1276, 1327, 1379,
];
```