Error

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 選擇性
人們可閱讀的錯誤說明。
fileName 選擇性 This API has not been standardized.
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 選擇性 This API has not been standardized.
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 Error.prototype (en-US).

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.

EvalError
Creates an instance representing an error that occurs regarding the global function eval() (en-US).
InternalError This API has not been standardized.
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() (en-US).
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() (en-US) or decodeURI() (en-US) are passed invalid parameters.

屬性

Error.prototype (en-US)
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

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

Error types

Besides the generic Error constructor, there are 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().
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.
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.
AggregateError
Creates an instance representing several errors wrapped in a single error when multiple errors need to be reported by an operation, for example by Promise.any().
InternalError This API has not been standardized.
Creates an instance representing an error that occurs when an internal error in the JavaScript engine is thrown. E.g. "too much recursion".

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 throw keyword. You can handle the error using the try...catch (en-US) 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 (en-US) property or, if you're writing for modern JavaScript engines, instanceof (en-US) 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.

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

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 (ECMA-262)
The definition of 'Error' in that specification.
Living Standard  

瀏覽器相容性

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help! (en-US)
Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

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