错误：cause

¥Value

在 options.cause 参数中传递给 Error() 构造函数的值。它可能不存在。

¥The value that was passed to the Error() constructor in the options.cause argument. It may not be present.

¥Description

cause 的值可以是任何类型。你不应该假设你捕获的错误的 cause 是 Error，就像你无法确定 catch 语句中绑定的变量是 Error 一样。下面的 "提供结构化数据作为错误原因" 示例显示了故意提供非错误作为原因的情况。

¥The value of cause can be of any type. You should not make assumptions that the error you caught has an Error as its cause, in the same way that you cannot be sure the variable bound in the catch statement is an Error either. The "Providing structured data as the error cause" example below shows a case where a non-error is deliberately provided as the cause.

¥Examples

¥Rethrowing an error with a cause

有时捕获错误并用新消息重新抛出它是有用的。在这种情况下，你应该将原始错误传递到新 Error 的构造函数中，如图所示。

¥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.

try {
  connectToDatabase();
} catch (err) {
  throw new Error("Connecting to database failed.", { cause: err });
}

有关更详细的示例，请参阅 错误 > 区分类似错误。

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

¥Providing structured data as the error cause

为人类使用而编写的错误消息可能不适合机器解析 - 因为它们会受到改写或标点符号更改的影响，这可能会破坏为使用它们而编写的任何现有解析。因此，当从函数抛出错误时，作为人类可读错误消息的替代方案，你可以将原因作为结构化数据提供，以供机器解析。

¥Error messages written for human consumption may be inappropriate for machine parsing — since they're subject to rewording or punctuation changes that may break any existing parsing written to consume them. So when throwing an error from a function, as an alternative to a human-readable error message, you can instead provide the cause as structured data, for machine parsing.

function makeRSA(p, q) {
  if (!Number.isInteger(p) || !Number.isInteger(q)) {
    throw new Error("RSA key generation requires integer inputs.", {
      cause: { code: "NonInteger", values: [p, q] },
    });
  }
  if (!areCoprime(p, q)) {
    throw new Error("RSA key generation requires two co-prime integers.", {
      cause: { code: "NonCoprime", values: [p, q] },
    });
  }
  // rsa algorithm…
}

¥See also

• Error.prototype.message
• Error.prototype.toString()