Error() constructor

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The Error() constructor creates Error objects.

Syntax

js
new Error()
new Error(message)
new Error(message, options)
new Error(message, fileName)
new Error(message, fileName, lineNumber)

Error()
Error(message)
Error(message, options)
Error(message, fileName)
Error(message, fileName, lineNumber)

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

Parameters

message Optional

A human-readable description of the error.

options Optional

An object that has the following properties:

cause Optional

A value indicating the specific cause of the error, reflected in the cause property. 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

The path to the file that raised this error, reflected in the fileName property. Defaults to the name of the file containing the code that called the Error() constructor.

lineNumber Optional

The line number within the file on which the error was raised, reflected in the lineNumber property. Defaults to the line number containing the Error() constructor invocation.

Examples

Function call or new construction

When Error is used like a function, that is without new, it will return an Error object. Therefore, a mere call to Error will produce the same output that constructing an Error object via the new keyword would.

js
const x = Error("I was created using a function call!");

// above has the same functionality as following
const y = new Error('I was constructed via the "new" keyword!');

Rethrowing an error with a cause

It is sometimes useful to catch an error and re-throw it with a new message. In this case you should pass the original error into the constructor for the new Error, as shown.

js
try {
  frameworkThatCanThrow();
} catch (err) {
  throw new Error("New error message", { cause: err });
}

For a more detailed example see Error > Differentiate between similar errors.

Omitting options argument

JavaScript only tries to read options.cause if options is an object — this avoids ambiguity with the other non-standard Error(message, fileName, lineNumber) signature, which requires the second parameter to be a string. If you omit options, pass a primitive value as options, or pass an object without the cause property, then the created Error object will have no cause property.

js
// Omitting options
const error1 = new Error("Error message");
console.log("cause" in error1); // false

// Passing a primitive value
const error2 = new Error("Error message", "");
console.log("cause" in error2); // false

// Passing an object without a cause property
const error3 = new Error("Error message", { details: "http error" });
console.log("cause" in error3); // false