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: Expected ':' (Edge)
SyntaxError: missing : after property id (Firefox)

Error type

SyntaxError

What went wrong?

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

var 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.

var 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.

var obj = { propertyKey: 'value' };

// or alternatively

var obj = { };
obj['propertyKey'] = 'value';

Empty properties

You can't create empty properties like this:

var obj = { propertyKey; };
// SyntaxError: missing : after property id

If you need to define a property without a value, you might use null as a value.

var obj = { propertyKey: null };

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:

var obj = { 'b'+'ar': 'foo' };
// SyntaxError: missing : after property id

Put the expression in brackets []:

var obj = { ['b'+'ar']: 'foo' };