--- title: Error slug: Web/JavaScript/Reference/Global_Objects/Error tags: - Error - JavaScript - NeedsTranslation - Reference - TopicStub translation_of: Web/JavaScript/Reference/Global_Objects/Error ---
{{JSRef}}

Error 建構函式能用來建立一個 error 物件。當執行期間發生錯誤時，Error 物件實體會被拋出。Error 物件也可作為自訂例外的基礎物件，請參考下方的標準內建錯誤類型。

語法

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

參數

message {{optional_inline}}
人們可閱讀的錯誤說明。
fileName {{optional_inline}} {{non-standard_inline}}
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_inline}} {{non-standard_inline}}
Optional. The value for the lineNumber property on the created Error object. Defaults to the line number containing the Error() constructor invocation.

描述

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 {{jsxref("Error.prototype")}}.

錯誤類型

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

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

屬性

{{jsxref("Error.prototype")}}
Allows the addition of properties to Error instances.

方法

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

Error 實體

{{page('en-US/docs/JavaScript/Reference/Global_Objects/Error/prototype', 'Description')}}

屬性

{{page('en-US/docs/JavaScript/Reference/Global_Objects/Error/prototype', 'Properties')}}

方法

{{page('en-US/docs/JavaScript/Reference/Global_Objects/Error/prototype', 'Methods')}}

範例

Throwing a generic error

Usually you create an Error object with the intention of raising it using the {{jsxref("Statements/throw", "throw")}} keyword. You can handle the error using the {{jsxref("Statements/try...catch", "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 {{jsxref("Object.prototype.constructor", "constructor")}} property or, if you're writing for modern JavaScript engines, {{jsxref("Operators/instanceof", "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. The common way to do this is demonstrated below.

Warning: Note that the thrown MyError will report incorrect lineNumber and fileName at least in Firefox.

See also the "What's a good way to extend Error in JavaScript?" discussion on Stackoverflow.

// Create a new object, that prototypically inherits from the Error constructor
function MyError(message) {
  this.name = 'MyError';
  this.message = message || 'Default Message';
  this.stack = (new Error()).stack;
}
MyError.prototype = Object.create(Error.prototype);
MyError.prototype.constructor = MyError;

try {
  throw new MyError();
} catch (e) {
  console.log(e.name);     // 'MyError'
  console.log(e.message);  // 'Default Message'
}

try {
  throw new MyError('custom message');
} catch (e) {
  console.log(e.name);     // 'MyError'
  console.log(e.message);  // 'custom message'
}

規範

{{Specifications}}

瀏覽器相容性

{{Compat}}

參見