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TypeError: invalid assignment to const "x" (Firefox)
TypeError: Assignment to constant variable. (Chrome)
TypeError: Assignment to const (Edge)
TypeError: Redeclaration of const 'x' (IE)

TypeError

JavaScript const

const COLUMNS = 80;

// ...

COLUMNS = 120; // TypeError: invalid assignment to const `COLUMNS'

const COLUMNS = 80;
const WIDE_COLUMNS = 120;

`constletvar`

const let var

let columns = 80;

// ...

let columns = 120;

const COLUMNS = 80;

function setupBigScreenEnvironment() {
  const COLUMNS = 120;
}

`const`

const

const obj = { foo: "bar" };
obj = { foo: "baz" }; // TypeError: invalid assignment to const `obj'

obj.foo = "baz";
obj; // Object { foo: "baz" }

const
let
var

MDN

MDN 2026217

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*