SyntaxError: missing : after property id

The JavaScript exception "missing : after property id" occurs when objects are created using the object initializer syntax. A colon (:) separates keys and values for the object's properties. Somehow, this colon is missing or misplaced.

Message#

SyntaxError: Invalid shorthand property initializer (V8-based)
SyntaxError: missing : after property id (Firefox)
SyntaxError: Unexpected token '='. Expected a ':' following the property name 'x'. (Safari)
SyntaxError: Unexpected token '+'. Expected an identifier as property name. (Safari)

Error type#

{{jsxref("SyntaxError")}}

What went wrong?#

When creating objects with the object initializer syntax, a colon (:) separates keys and values for the object's properties.

const obj = { propertyKey: "value" };

Examples#

Colons vs. equal signs#

This code fails, as the equal sign can't be used this way in this object initializer syntax.

```js-nolint example-bad const obj = { propertyKey = "value" }; // SyntaxError: missing : after property id

Correct would be to use a colon, or to use square brackets to assign a new property
after the object has been created already.

```js example-good
const obj = { propertyKey: "value" };

Or alternatively:

const obj = {};
obj.propertyKey = "value";

Computed properties#

If you create a property key from an expression, you need to use square brackets. Otherwise the property name can't be computed:

```js-nolint example-bad const obj = { "b"+"ar": "foo" }; // SyntaxError: missing : after property id

Put the expression in square brackets `[]`:

```js example-good
const obj = { ["b" + "ar"]: "foo" };

See also#

• Object initializer