SyntaxError: Unexpected '#' used outside of class body

The JavaScript exception "Unexpected '#' used outside of class body" occurs when a hash ("#") is encountered in an unexpected context, most notably outside of a class declaration. Hashes are valid at the beginning of a file as a hashbang comment, or inside of a class as part of a private field. You may encounter this error if you forget the quotation marks when trying to access a DOM identifier as well.

Message#

SyntaxError: Unexpected '#' used outside of class body.

Error type#

{{jsxref("SyntaxError")}}

What went wrong?#

We encountered a # somewhere unexpected. This may be due to code moving around and no longer being part of a class, a hashbang comment found on a line other than the first line of a file, or accidentally forgetting the quotation marks around a DOM identifier.

Examples#

Missing quotation marks#

For each case, there might be something slightly wrong. For example

```js-nolint example-bad document.querySelector(#some-element)

This can be fixed via

```js example-good
document.querySelector("#some-element");

Outside of a class#

```js-nolint example-bad class ClassWithPrivateField { #privateField;

constructor() {} }

this.#privateField = 42;

This can be fixed by moving the private field back into the class

```js example-good
class ClassWithPrivateField {
  #privateField;

  constructor() {
    this.#privateField = 42;
  }
}

See also#

• {{jsxref("SyntaxError")}}