SyntaxError: missing variable name

The JavaScript exception "missing variable name" is a common error experienced by developers. It mostly occurs due to a typo or a forgotten variable name.

Message

SyntaxError: missing variable name (Firefox)
SyntaxError: Unexpected token = (Chrome)

Error type

SyntaxError

What went wrong?

A variable is missing a name. The cause is most likely a typo or a forgotten variable name. Make sure that you've provided the name of the variable before the = sign.

When declaring multiple variables at the same time, make sure that the previous lines/declaration does not end with a comma instead of a semi-colon.

Examples

Missing a variable name

var = "foo";

Coming up with a descriptive variable name is challenging for most developers. It gets easier over time.

var description = "foo";

Reserved keywords can't be variable names

There are a few variable names that are reserved keywords. You can't use these. Sorry :(

var debugger = "whoop";
// SyntaxError: missing variable name

Declaring multiple variables

Pay special attention to commas when declaring multiple variables. Is there an excess comma? Did you accidentally add commas instead of semicolons?

var x, y = "foo",
var x, = "foo"

var first = document.getElementById('one'),
var second = document.getElementById('two'),

// SyntaxError: missing variable name

The fixed version:

var x, y = "foo";
var x = "foo";

var first = document.getElementById('one');
var second = document.getElementById('two');

Arrays

Array literals in JavaScript need square brackets around the values. This won't work:

var arr = 1,2,3,4,5;
// SyntaxError: missing variable name

This would be correct:

var arr = [1,2,3,4,5];