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!
- 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: 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: reference to undefined property "x"
- SyntaxError: "0"-prefixed octal literals and octal escape seq. are deprecated
- SyntaxError: "use strict" not allowed in function with non-simple parameters
- SyntaxError: "x" is a reserved identifier
- 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: 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: await is only valid in async functions, async generators and modules
- SyntaxError: cannot use `??` unparenthesized within `||` and `&&` expressions
- SyntaxError: continue must be inside loop
- SyntaxError: for-in loop head declarations may not have initializers
- SyntaxError: function statement requires a name
- SyntaxError: identifier starts immediately after numeric literal
- SyntaxError: illegal character
- SyntaxError: invalid BigInt syntax
- SyntaxError: invalid assignment left-hand side
- SyntaxError: invalid regular expression flag "x"
- SyntaxError: label not found
- SyntaxError: missing ) after argument list
- SyntaxError: missing ) after condition
- SyntaxError: missing : after property id
- SyntaxError: missing ; before statement
- 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: redeclaration of formal parameter "x"
- SyntaxError: return not in function
- SyntaxError: test for equality (==) mistyped as assignment (=)?
- SyntaxError: unlabeled break must be inside loop or switch
- SyntaxError: unparenthesized unary expression can't appear on the left-hand side of '**'
- SyntaxError: unterminated string literal
- TypeError: "x" has no properties
- 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: More arguments needed
- TypeError: Reduce of empty array with no initial value
- TypeError: X.prototype.y called on incompatible type
- 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: cannot use 'in' operator to search for 'x' in 'y'
- TypeError: cyclic object value
- TypeError: invalid 'instanceof' operand 'x'
- TypeError: invalid Array.prototype.sort argument
- TypeError: invalid assignment to const "x"
- 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