Throw new typeerror javascript

TypeError

Объект TypeError представляет ошибку, возникающую, когда значение имеет не ожидаемый тип.

Синтаксис

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

Параметры

Необязательный параметр. Человеко-читаемое описание ошибки.

Необязательный параметр. Имя файла, содержащего код, вызвавший исключение.

Необязательный параметр. Номер строки кода, вызвавшей исключение.

Описание

Исключение TypeError выбрасывается, когда операнд или аргумент, переданный в функцию, не совместим с типом, ожидаемым оператором или функцией.

Свойства

Позволяет добавлять свойства в объект TypeError .

Методы

Глобальный объект TypeError не содержит собственных методов, однако, он наследует некоторые методы из цепочки прототипов.

Экземпляры объекта TypeError

Свойства

Методы

Примеры

Пример: перехват исключения TypeError

try  null.f(); > catch (e)  console.log(e instanceof TypeError); // true console.log(e.message); // "null has no properties" - null не имеет свойств console.log(e.name); // "TypeError" console.log(e.fileName); // "Scratchpad/1" console.log(e.lineNumber); // 2 console.log(e.columnNumber); // 2 console.log(e.stack); // "@Scratchpad/2:2:3\n" > 

Пример: возбуждение исключения TypeError

try  throw new TypeError('Привет', 'someFile.js', 10); > catch (e)  console.log(e instanceof TypeError); // true console.log(e.message); // "Привет" console.log(e.name); // "TypeError" console.log(e.fileName); // "someFile.js" console.log(e.lineNumber); // 10 console.log(e.columnNumber); // 0 console.log(e.stack); // "@Scratchpad/2:2:9\n" > 

Спецификации

Совместимость с браузерами

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throw

The throw statement throws a user-defined exception. Execution of the current function will stop (the statements after throw won’t be executed), and control will be passed to the first catch block in the call stack. If no catch block exists among caller functions, the program will terminate.

Try it

Syntax

Description

The throw statement is valid in all contexts where statements can be used. Its execution generates an exception that penetrates through the call stack. For more information on error bubbling and handling, see Control flow and error handling.

The throw keyword can be followed by any kind of expression, for example:

throw error; // Throws a previously defined value (e.g. within a catch block) throw new Error("Required"); // Throws a new Error object 

In practice, the exception you throw should always be an Error object or an instance of an Error subclass, such as RangeError . This is because code that catches the error may expect certain properties, such as message , to be present on the caught value. For example, web APIs typically throw DOMException instances, which inherit from Error.prototype .

Automatic semicolon insertion

The syntax forbids line terminators between the throw keyword and the expression to be thrown.

The code above is transformed by automatic semicolon insertion (ASI) into:

This is invalid code, because unlike return , throw must be followed by an expression.

To avoid this problem (to prevent ASI), you could use parentheses:

Examples

Throwing a user-defined error

This example defines a function that throws a TypeError if the input is not of the expected type.

function isNumeric(x)  return ["number", "bigint"].includes(typeof x); > function sum(. values)  if (!values.every(isNumeric))  throw new TypeError("Can only add numbers"); > return values.reduce((a, b) => a + b); > console.log(sum(1, 2, 3)); // 6 try  sum("1", "2"); > catch (e)  console.error(e); // TypeError: Can only add numbers > 

Throwing an existing object

This example calls a callback-based async function, and throws an error if the callback receives an error.

readFile("foo.txt", (err, data) =>  if (err)  throw err; > console.log(data); >); 

Errors thrown this way are not catchable by the caller and will cause the program to crash unless (a) the readFile function itself catches the error, or (b) the program is running in a context that catches top-level errors. You can handle errors more naturally by using the Promise() constructor.

function readFilePromise(path)  return new Promise((resolve, reject) =>  readFile(path, (err, data) =>  if (err)  reject(err); > resolve(data); >); >); > try  const data = await readFilePromise("foo.txt"); console.log(data); > catch (err)  console.error(err); > 

Specifications

Browser compatibility

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See also

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TypeError() constructor

The TypeError() constructor creates TypeError objects.

Syntax

new TypeError() new TypeError(message) new TypeError(message, options) new TypeError(message, fileName) new TypeError(message, fileName, lineNumber) TypeError() TypeError(message) TypeError(message, options) TypeError(message, fileName) TypeError(message, fileName, lineNumber) 

Note: TypeError() can be called with or without new . Both create a new TypeError instance.

Parameters

Human-readable description of the error

An object that has the following properties:

A property indicating the specific cause of the error. When catching and re-throwing an error with a more-specific or useful error message, this property can be used to pass the original error.

fileName Optional Non-standard

The name of the file containing the code that caused the exception

lineNumber Optional Non-standard

The line number of the code that caused the exception

Examples

Catching a TypeError

try  null.f(); > catch (e)  console.log(e instanceof TypeError); // true console.log(e.message); // "null has no properties" console.log(e.name); // "TypeError" console.log(e.stack); // Stack of the error > 

Creating a TypeError

try  throw new TypeError("Hello"); > catch (e)  console.log(e instanceof TypeError); // true console.log(e.message); // "Hello" console.log(e.name); // "TypeError" console.log(e.stack); // Stack of the error > 

Specifications

Browser compatibility

BCD tables only load in the browser

See also

Found a content problem with this page?

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TypeError

The TypeError object represents an error when an operation could not be performed, typically (but not exclusively) when a value is not of the expected type.

A TypeError may be thrown when:

• an operand or argument passed to a function is incompatible with the type expected by that operator or function; or
• when attempting to modify a value that cannot be changed; or
• when attempting to use a value in an inappropriate way.

Constructor

Creates a new TypeError object.

Instance properties

Error message. Although ECMA-262 specifies that TypeError should provide its own message property, in SpiderMonkey, it inherits Error.prototype.message .

Error name. Inherited from Error .

Path to file that raised this error. Inherited from Error .

Line number in file that raised this error. Inherited from Error .

Column number in line that raised this error. Inherited from Error .

Stack trace. Inherited from Error .

Examples

Catching a TypeError

try  null.f() > catch (e)  console.log(e instanceof TypeError) // true console.log(e.message) // "null has no properties" console.log(e.name) // "TypeError" console.log(e.fileName) // "Scratchpad/1" console.log(e.lineNumber) // 2 console.log(e.columnNumber) // 2 console.log(e.stack) // "@Scratchpad/2:2:3\n" > 

Creating a TypeError

try  throw new TypeError('Hello', "someFile.js", 10) > catch (e)  console.log(e instanceof TypeError) // true console.log(e.message) // "Hello" console.log(e.name) // "TypeError" console.log(e.fileName) // "someFile.js" console.log(e.lineNumber) // 10 console.log(e.columnNumber) // 0 console.log(e.stack) // "@Scratchpad/2:2:9\n" > 

Specifications

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