SyntaxError: arguments is not valid in fields
The JavaScript exception "SyntaxError: arguments is not valid in fields" occurs when thearguments identifier is read in a class field initializer or in a static initialization block, outside of a non-arrow function.
Message
SyntaxError: 'arguments' is not allowed in class field initializer or static initialization block (V8-based)SyntaxError: arguments is not valid in fields (Firefox)SyntaxError: Unexpected identifier 'arguments'. Cannot reference 'arguments' in class field initializer. (Safari)
Error type
What went wrong?
A class field initializer expression or a class static initialization block does not havearguments in its scope. Trying to access it is a syntax error.
- This is true even if
argumentsis bound in a parent scope (such as when the class is nested in a non-arrow function). - A non-arrow function declared within this scope will still bind its own
argumentsand read it normally.
Examples
js
function makeOne() { class C { args = { ...arguments }; // SyntaxError: arguments is not valid in fields } return new C();}js
let CArgs;class C { static { CArgs = arguments; // SyntaxError: arguments is not valid in fields }}js
class C { args = {}; constructor() { this.args = arguments; // You can use arguments in constructors } myMethod() { this.args = arguments; // You can also use it in methods }}js
function makeOne() { const _arguments = arguments; class C { args = { ..._arguments }; // Only the identifier is forbidden } return new C();}