JavaScript error reference
Below, you'll find a list of errors which are thrown by JavaScript. These errors can be a helpful debugging aid, but the reported problem isn't always immediately clear. The pages below will provide additional details about these errors. Each error is an object based upon the Error object, and has a name and a message.
Errors displayed in the Web console may include a link to the corresponding page below to help you quickly comprehend the problem in your code.
For a beginner's introductory tutorial on fixing JavaScript errors, see What went wrong? Troubleshooting JavaScript.
List of errors
In this list, each page is listed by name (the type of error) and message (a more detailed human-readable error message). Together, these two properties provide a starting point toward understanding and resolving the error. For more information, follow the links below!
- AggregateError: No Promise in Promise.any was resolved
- Error: Permission denied to access property "x"
- InternalError: too much recursion
- RangeError: BigInt division by zero
- RangeError: BigInt negative exponent
- RangeError: argument is not a valid code point
- RangeError: form must be one of 'NFC', 'NFD', 'NFKC', or 'NFKD'
- RangeError: invalid array length
- RangeError: invalid date
- RangeError: precision is out of range
- RangeError: radix must be an integer
- RangeError: repeat count must be less than infinity
- RangeError: repeat count must be non-negative
- RangeError: x can't be converted to BigInt because it isn't an integer
- ReferenceError: "x" is not defined
- ReferenceError: assignment to undeclared variable "x"
- ReferenceError: can't access lexical declaration 'X' before initialization
- ReferenceError: deprecated caller or arguments usage
- ReferenceError: must call super constructor before using 'this' in derived class constructor
- ReferenceError: super() called twice in derived class constructor
- SyntaxError: "0"-prefixed octal literals are deprecated
- SyntaxError: "use strict" not allowed in function with non-simple parameters
- SyntaxError: "x" is a reserved identifier
- SyntaxError: 'arguments'/'eval' can't be defined or assigned to in strict mode code
- SyntaxError: JSON.parse: bad parsing
- SyntaxError: Unexpected '#' used outside of class body
- SyntaxError: Unexpected token
- SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead
- SyntaxError: \ at end of pattern
- SyntaxError: a declaration in the head of a for-of loop can't have an initializer
- SyntaxError: applying the 'delete' operator to an unqualified name is deprecated
- SyntaxError: arguments is not valid in fields
- SyntaxError: await is only valid in async functions, async generators and modules
- SyntaxError: await/yield expression can't be used in parameter
- SyntaxError: cannot use `??` unparenthesized within `||` and `&&` expressions
- SyntaxError: character class escape cannot be used in class range in regular expression
- SyntaxError: continue must be inside loop
- SyntaxError: duplicate capture group name in regular expression
- SyntaxError: duplicate formal argument x
- SyntaxError: for-in loop head declarations may not have initializers
- SyntaxError: function statement requires a name
- SyntaxError: functions cannot be labelled
- SyntaxError: getter and setter for private name #x should either be both static or non-static
- SyntaxError: getter functions must have no arguments
- SyntaxError: identifier starts immediately after numeric literal
- SyntaxError: illegal character
- SyntaxError: import declarations may only appear at top level of a module
- SyntaxError: incomplete quantifier in regular expression
- SyntaxError: invalid BigInt syntax
- SyntaxError: invalid assignment left-hand side
- SyntaxError: invalid capture group name in regular expression
- SyntaxError: invalid character in class in regular expression
- SyntaxError: invalid class set operation in regular expression
- SyntaxError: invalid decimal escape in regular expression
- SyntaxError: invalid identity escape in regular expression
- SyntaxError: invalid named capture reference in regular expression
- SyntaxError: invalid property name in regular expression
- SyntaxError: invalid range in character class
- SyntaxError: invalid regexp group
- SyntaxError: invalid regular expression flag "x"
- SyntaxError: invalid unicode escape in regular expression
- SyntaxError: label not found
- SyntaxError: missing ) after argument list
- SyntaxError: missing ) after condition
- SyntaxError: missing : after property id
- SyntaxError: missing = in const declaration
- SyntaxError: missing ] after element list
- SyntaxError: missing formal parameter
- SyntaxError: missing name after . operator
- SyntaxError: missing variable name
- SyntaxError: missing } after function body
- SyntaxError: missing } after property list
- SyntaxError: negated character class with strings in regular expression
- SyntaxError: new keyword cannot be used with an optional chain
- SyntaxError: nothing to repeat
- SyntaxError: numbers out of order in {} quantifier.
- SyntaxError: octal escape sequences can't be used in untagged template literals or in strict mode code
- SyntaxError: parameter after rest parameter
- SyntaxError: private fields can't be deleted
- SyntaxError: property name __proto__ appears more than once in object literal
- SyntaxError: raw bracket is not allowed in regular expression with unicode flag
- SyntaxError: redeclaration of formal parameter "x"
- SyntaxError: reference to undeclared private field or method #x
- SyntaxError: rest parameter may not have a default
- SyntaxError: return not in function
- SyntaxError: setter functions must have one argument
- SyntaxError: string literal contains an unescaped line break
- SyntaxError: super() is only valid in derived class constructors
- SyntaxError: tagged template cannot be used with optional chain
- SyntaxError: unlabeled break must be inside loop or switch
- SyntaxError: unparenthesized unary expression can't appear on the left-hand side of '**'
- SyntaxError: use of super property/member accesses only valid within methods or eval code within methods
- TypeError: "x" is (not) "y"
- TypeError: "x" is not a constructor
- TypeError: "x" is not a function
- TypeError: "x" is not a non-null object
- TypeError: "x" is read-only
- TypeError: 'x' is not iterable
- TypeError: BigInt value can't be serialized in JSON
- TypeError: Initializing an object twice is an error with private fields/methods
- TypeError: Iterator/AsyncIterator constructor can't be used directly
- TypeError: More arguments needed
- TypeError: Reduce of empty array with no initial value
- TypeError: WeakSet key/WeakMap value 'x' must be an object or an unregistered symbol
- TypeError: X.prototype.y called on incompatible type
- TypeError: calling a builtin X constructor without new is forbidden
- TypeError: can't access/set private field or method: object is not the right class
- TypeError: can't assign to property "x" on "y": not an object
- TypeError: can't convert BigInt to number
- TypeError: can't convert x to BigInt
- TypeError: can't define property "x": "obj" is not extensible
- TypeError: can't delete non-configurable array element
- TypeError: can't redefine non-configurable property "x"
- TypeError: can't set prototype of this object
- TypeError: can't set prototype: it would cause a prototype chain cycle
- TypeError: cannot use 'in' operator to search for 'x' in 'y'
- TypeError: class constructors must be invoked with 'new'
- TypeError: cyclic object value
- TypeError: derived class constructor returned invalid value x
- TypeError: getting private setter-only property
- TypeError: invalid 'instanceof' operand 'x'
- TypeError: invalid Array.prototype.sort argument
- TypeError: invalid assignment to const "x"
- TypeError: matchAll/replaceAll must be called with a global RegExp
- TypeError: null/undefined has no properties
- TypeError: property "x" is non-configurable and can't be deleted
- TypeError: setting getter-only property "x"
- URIError: malformed URI sequence
- Warning: -file- is being assigned a //# sourceMappingURL, but already has one
- Warning: unreachable code after return statement