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
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
document.querySelector(#some-element)
This can be fixed via
js
document.querySelector("#some-element");
Outside of a class
js
class ClassWithPrivateField {
#privateField;
constructor() {}
}
this.#privateField = 42;
This can be fixed by moving the private field back into the class
js
class ClassWithPrivateField {
#privateField;
constructor() {
this.#privateField = 42;
}
}