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The Error constructor creates an error object. Instances of Error objects are thrown when runtime errors occur. The Error object can also be used as a base object for user-defined exceptions. See below for standard built-in error types.

Syntax

new Error([message[, fileName[, lineNumber]]])

Parameters

message
Optional. Human-readable description of the error.
fileName
Optional. The value for the fileName property on the created Error object. Defaults to the name of the file containing the code that called the Error() constructor.
lineNumber
Optional. The value for the lineNumber property on the created Error object. Defaults to the line number containing the Error() constructor invocation.

Description

Runtime errors result in new Error objects being created and thrown.

This page documents the use of the Error object itself and its use as a constructor function. For a list of properties and methods inherited by Error instances, see Error.prototype.

Error types

Besides the generic Error constructor, there are seven other core error constructors in JavaScript. For client-side exceptions, see Exception Handling Statements.

EvalError
Creates an instance representing an error that occurs regarding the global function eval().
InternalError
Creates an instance representing an error that occurs when an internal error in the JavaScript engine is thrown. E.g. "too much recursion".
RangeError
Creates an instance representing an error that occurs when a numeric variable or parameter is outside of its valid range.
ReferenceError
Creates an instance representing an error that occurs when de-referencing an invalid reference.
SyntaxError
Creates an instance representing a syntax error that occurs while parsing code in eval().
TypeError
Creates an instance representing an error that occurs when a variable or parameter is not of a valid type.
URIError
Creates an instance representing an error that occurs when encodeURI() or decodeURI() are passed invalid parameters.

Properties

Error.prototype
Allows the addition of properties to Error instances.

Methods

The global Error object contains no methods of its own, however, it does inherit some methods through the prototype chain.

Error instances

All Error instances and instances of non-generic errors inherit from Error.prototype. As with all constructor functions, you can use the prototype of the constructor to add properties or methods to all instances created with that constructor.

Properties

Standard properties

Error.prototype.constructor
Specifies the function that created an instance's prototype.
Error.prototype.message
Error message.
Error.prototype.name
Error name.

Vendor-specific extensions

Non-standard
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

Microsoft

Error.prototype.description
Error description. Similar to message.
Error.prototype.number
Error number.

Mozilla

Error.prototype.fileName
Path to file that raised this error.
Error.prototype.lineNumber
Line number in file that raised this error.
Error.prototype.columnNumber
Column number in line that raised this error.
Error.prototype.stack
Stack trace.

Methods

Error.prototype.toSource()
Returns a string containing the source of the specified Error object; you can use this value to create a new object. Overrides the Object.prototype.toSource() method.
Error.prototype.toString()
Returns a string representing the specified object. Overrides the Object.prototype.toString() method.

Examples

Throwing a generic error

Usually you create an Error object with the intention of raising it using the throw keyword. You can handle the error using the try...catch construct:

try {
  throw new Error('Whoops!');
} catch (e) {
  console.log(e.name + ': ' + e.message);
}

Handling a specific error

You can choose to handle only specific error types by testing the error type with the error's constructor property or, if you're writing for modern JavaScript engines, instanceof keyword:

try {
  foo.bar();
} catch (e) {
  if (e instanceof EvalError) {
    console.log(e.name + ': ' + e.message);
  } else if (e instanceof RangeError) {
    console.log(e.name + ': ' + e.message);
  }
  // ... etc
}

Custom Error Types

You might want to define your own error types deriving from Error to be able to throw new MyError() and use instanceof MyError to check the kind of error in the exception handler.  This results in cleaner and more consistent error handling code.  See "What's a good way to extend Error in JavaScript?" on StackOverflow for an in-depth discussion.

ES6 Custom Error Class

Babel and other transpilers will not correctly handle the following code without additional configuration.

Some browsers include the CustomError constructor in the stacktrace when using ES6 classes.

class CustomError extends Error {
  constructor(foo = 'bar', ...params) {
    // Pass remaining arguments (including vendor specific ones) to parent constructor
    super(...params);

    // Maintains proper stack trace for where our error was thrown
    Error.captureStackTrace(this, CustomError);

    // Custom debugging information
    this.foo = foo;
    this.date = new Date();
  }
}

try {
  throw new CustomError('baz', 'bazMessage');
} catch(e){
  console.log(e.foo); //baz
  console.log(e.message); //bazMessage
  console.log(e.stack); //stacktrace
}

ES5 Custom Error Object

All browsers include the CustomError constructor in the stacktrace when using a prototypal declaration.

function CustomError(foo, message, fileName, lineNumber) {
  var instance = new Error(message, fileName, lineNumber);
  instance.foo = foo;
  Object.setPrototypeOf(instance, Object.getPrototypeOf(this));
  Error.captureStackTrace(instance, CustomError);
  return instance;
}

CustomError.prototype = Object.create(Error.prototype, {
  constructor: {
    value: Error,
    enumerable: false,
    writable: true,
    configurable: true
  }
});

if (Object.setPrototypeOf){
  Object.setPrototypeOf(CustomError, Error);
} else {
  CustomError.__proto__ = Error;
}


try {
  throw new CustomError('baz', 'bazMessage');
} catch(e){
  console.log(e.foo); //baz
  console.log(e.message) ;//bazMessage
}

Specifications

Specification Status Comment
ECMAScript 1st Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.1.
ECMAScript 5.1 (ECMA-262)
The definition of 'Error' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Error' in that specification.
Standard  
ECMAScript Latest Draft (ECMA-262)
The definition of 'Error' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic Support (Yes) (Yes) (Yes)6 (Yes) (Yes)
prototype (Yes) (Yes) (Yes)6 (Yes) (Yes)
columnNumber No No (Yes) No No No
fileName No No (Yes) No No No
lineNumber No No (Yes) No No No
message (Yes) (Yes) (Yes)6 (Yes) (Yes)
name (Yes) (Yes) (Yes)6 (Yes) (Yes)
stack (Yes) (Yes) (Yes)10 (Yes)6
toSource No No (Yes) No No No
toString (Yes) (Yes) (Yes)6 (Yes) (Yes)
FeatureAndroidChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic Support (Yes) (Yes) (Yes) (Yes)8.1 (Yes) (Yes)
prototype (Yes) (Yes) (Yes) (Yes)8.1 (Yes) (Yes)
columnNumber No No No (Yes) No No No
fileName No No No (Yes) No No No
lineNumber No No No (Yes) No No No
message (Yes) (Yes) (Yes) (Yes)8.1 (Yes) (Yes)
name (Yes) (Yes) (Yes) (Yes)8.1 (Yes) (Yes)
stack (Yes) (Yes) (Yes) (Yes) ? (Yes)6
toSource No No No (Yes) No No No
toString (Yes) (Yes) (Yes) (Yes)8.1 (Yes) (Yes)

See also