: |

Baseline

20157

regex

alternative1|alternative2
alternative1|alternative2|alternative3|

alternativeN: 1

| 2 2 "ab" "a"

/a|ab/.exec("abc"); // ['a']

|

/(?:(a)|(ab))(?:(c)|(bc))/.exec("abc"); // ['abc', 'a', undefined, undefined, 'bc']
// Not ['abc', undefined, 'ab', 'c', undefined]

a 2 bc

undefined

function isImage(filename) {
  return /\.(?:png|jpe?g|webp|avif|gif)$/i.test(filename);
}

isImage("image.png"); // true
isImage("image.jpg"); // true
isImage("image.pdf"); // false


ECMAScript 2027 LanguageSpecification # prod-Disjunction

: *, +, ?, {n}, {n,}, {n,m}
: [...], [^...]

MDN

MDN 2023814

GitHub

JavaScript
JavaScript
1. (+)
2. (+=)
3. (=)
4. async function
5. async function*
6. await
7. (&)
8. (&=)
9. (~)
10. (|)
11. (|=)
12. (^)
13. (^=)
14. class
15. (,)
17. (--)
18. delete
20. (/)
21. (/=)
22. (==)
23. (**)
24. (**=)
25. function
26. function*
27. (>)
28. (>=)
29. ( )
30. import.meta
  1. import.meta.resolve()
31. import()
32. in
33. (++)
34. (!=)
35. instanceof
36. (<<)
37. (<<=)
38. (<)
39. (<=)
40. (&&)
41. (&&=)
42. (!)
43. (||)
44. (||=)
45. (*)
46. (*=)
47. new
48. new.target
49. null
50. (??=)
51. (??)
54. (?.)
56. (%)
57. (%=)
58. (>>)
59. (>>=)
60. (...)
61. (===)
62. (!==)
63. (-)
64. (-=)
65. super
66. this
67. typeof
68. (-)
69. (+)
70. (>>>)
71. (>>>=)
72. void
73. yield
74. yield*