SyntaxError: missing = in const declaration

The JavaScript exception "missing = in const declaration" occurs when a const declaration was not given a value in the same statement (like const RED_FLAG;). You need to provide one (const RED_FLAG = true).

Message#

SyntaxError: Missing initializer in const declaration (V8-based)
SyntaxError: missing = in const declaration (Firefox)
SyntaxError: Unexpected token ';'. const declared variable 'x' must have an initializer. (Safari)

Error type#

{{jsxref("SyntaxError")}}

What went wrong?#

A constant is a value that cannot be altered by the program during normal execution. It cannot change through re-assignment, and it can't be redeclared. In JavaScript, constants are declared using the const keyword. An initializer for a constant is required; that is, you must specify its value in the same statement in which it's declared (which makes sense, given that it can't be changed later).

Examples#

Missing const initializer#

Unlike var or let, you must specify a value for a const declaration. This throws:

```js-nolint example-bad const COLUMNS; // SyntaxError: missing = in const declaration

### Fixing the error

There are multiple options to fix this error. Check what was intended to be achieved
with the constant in question.

#### Adding a constant value

Specify the constant value in the same statement in which it's declared:

```js example-good
const COLUMNS = 80;

const, let or var?#

Do not use const if you weren't meaning to declare a constant. Maybe you meant to declare a block-scoped variable with let or global variable with var. Both don't require an initial value.

js example-good let columns;

See also#

• const
• let
• var