assert.throws(fn[, error][, message])

• fn <Function>
• error <RegExp> | <Function> | <Object> | <Error>
• message <string>

期望函数 fn 抛出一个错误。

【Expects the function fn to throw an error.】

如果指定，error 可以是 Class、<RegExp>、一个验证函数、一个验证对象（其中每个属性将进行严格的深度相等性检查），或者一个错误实例（其中每个属性都将进行严格的深度相等性检查，包括不可枚举的 message 和 name 属性）。在使用对象时，也可以在验证字符串属性时使用正则表达式。示例如下。

【If specified, error can be a Class, <RegExp>, a validation function, a validation object where each property will be tested for strict deep equality, or an instance of error where each property will be tested for strict deep equality including the non-enumerable message and name properties. When using an object, it is also possible to use a regular expression, when validating against a string property. See below for examples.】

如果指定，message 将会被附加到 AssertionError 提供的消息中，当 fn 调用未抛出异常或在错误验证失败时。

【If specified, message will be appended to the message provided by the AssertionError if the fn call fails to throw or in case the error validation fails.】

自定义验证对象/错误实例：

【Custom validation object/error instance:】

import assert from 'node:assert/strict';

const err = new TypeError('Wrong value');
err.code = 404;
err.foo = 'bar';
err.info = {
  nested: true,
  baz: 'text',
};
err.reg = /abc/i;

assert.throws(
  () => {
    throw err;
  },
  {
    name: 'TypeError',
    message: 'Wrong value',
    info: {
      nested: true,
      baz: 'text',
    },
    // Only properties on the validation object will be tested for.
    // Using nested objects requires all properties to be present. Otherwise
    // the validation is going to fail.
  },
);

// Using regular expressions to validate error properties:
assert.throws(
  () => {
    throw err;
  },
  {
    // The `name` and `message` properties are strings and using regular
    // expressions on those will match against the string. If they fail, an
    // error is thrown.
    name: /^TypeError$/,
    message: /Wrong/,
    foo: 'bar',
    info: {
      nested: true,
      // It is not possible to use regular expressions for nested properties!
      baz: 'text',
    },
    // The `reg` property contains a regular expression and only if the
    // validation object contains an identical regular expression, it is going
    // to pass.
    reg: /abc/i,
  },
);

// Fails due to the different `message` and `name` properties:
assert.throws(
  () => {
    const otherErr = new Error('Not found');
    // Copy all enumerable properties from `err` to `otherErr`.
    for (const [key, value] of Object.entries(err)) {
      otherErr[key] = value;
    }
    throw otherErr;
  },
  // The error's `message` and `name` properties will also be checked when using
  // an error as validation object.
  err,
);const assert = require('node:assert/strict');

const err = new TypeError('Wrong value');
err.code = 404;
err.foo = 'bar';
err.info = {
  nested: true,
  baz: 'text',
};
err.reg = /abc/i;

assert.throws(
  () => {
    throw err;
  },
  {
    name: 'TypeError',
    message: 'Wrong value',
    info: {
      nested: true,
      baz: 'text',
    },
    // Only properties on the validation object will be tested for.
    // Using nested objects requires all properties to be present. Otherwise
    // the validation is going to fail.
  },
);

// Using regular expressions to validate error properties:
assert.throws(
  () => {
    throw err;
  },
  {
    // The `name` and `message` properties are strings and using regular
    // expressions on those will match against the string. If they fail, an
    // error is thrown.
    name: /^TypeError$/,
    message: /Wrong/,
    foo: 'bar',
    info: {
      nested: true,
      // It is not possible to use regular expressions for nested properties!
      baz: 'text',
    },
    // The `reg` property contains a regular expression and only if the
    // validation object contains an identical regular expression, it is going
    // to pass.
    reg: /abc/i,
  },
);

// Fails due to the different `message` and `name` properties:
assert.throws(
  () => {
    const otherErr = new Error('Not found');
    // Copy all enumerable properties from `err` to `otherErr`.
    for (const [key, value] of Object.entries(err)) {
      otherErr[key] = value;
    }
    throw otherErr;
  },
  // The error's `message` and `name` properties will also be checked when using
  // an error as validation object.
  err,
);拷贝

使用构造函数验证 instanceof：

【Validate instanceof using constructor:】

import assert from 'node:assert/strict';

assert.throws(
  () => {
    throw new Error('Wrong value');
  },
  Error,
);const assert = require('node:assert/strict');

assert.throws(
  () => {
    throw new Error('Wrong value');
  },
  Error,
);拷贝

使用 <RegExp> 验证错误消息：

【Validate error message using <RegExp>:】

使用正则表达式会对错误对象运行 .toString，因此也会包含错误名称。

【Using a regular expression runs .toString on the error object, and will therefore also include the error name.】

import assert from 'node:assert/strict';

assert.throws(
  () => {
    throw new Error('Wrong value');
  },
  /^Error: Wrong value$/,
);const assert = require('node:assert/strict');

assert.throws(
  () => {
    throw new Error('Wrong value');
  },
  /^Error: Wrong value$/,
);拷贝

自定义错误验证：

【Custom error validation:】

该函数必须返回 true 以表示所有内部验证通过。否则将以 AssertionError 失败。

【The function must return true to indicate all internal validations passed. It will otherwise fail with an AssertionError.】

import assert from 'node:assert/strict';

assert.throws(
  () => {
    throw new Error('Wrong value');
  },
  (err) => {
    assert(err instanceof Error);
    assert(/value/.test(err));
    // Avoid returning anything from validation functions besides `true`.
    // Otherwise, it's not clear what part of the validation failed. Instead,
    // throw an error about the specific validation that failed (as done in this
    // example) and add as much helpful debugging information to that error as
    // possible.
    return true;
  },
  'unexpected error',
);const assert = require('node:assert/strict');

assert.throws(
  () => {
    throw new Error('Wrong value');
  },
  (err) => {
    assert(err instanceof Error);
    assert(/value/.test(err));
    // Avoid returning anything from validation functions besides `true`.
    // Otherwise, it's not clear what part of the validation failed. Instead,
    // throw an error about the specific validation that failed (as done in this
    // example) and add as much helpful debugging information to that error as
    // possible.
    return true;
  },
  'unexpected error',
);拷贝

error 不能是字符串。如果第二个参数提供的是字符串，则假定省略了 error，该字符串将用于 message。这可能会导致容易被忽略的错误。使用与抛出的错误消息相同的消息将导致 ERR_AMBIGUOUS_ARGUMENT 错误。如果将字符串作为第二个参数，请仔细阅读下面的示例：

import assert from 'node:assert/strict';

function throwingFirst() {
  throw new Error('First');
}

function throwingSecond() {
  throw new Error('Second');
}

function notThrowing() {}

// The second argument is a string and the input function threw an Error.
// The first case will not throw as it does not match for the error message
// thrown by the input function!
assert.throws(throwingFirst, 'Second');
// In the next example the message has no benefit over the message from the
// error and since it is not clear if the user intended to actually match
// against the error message, Node.js throws an `ERR_AMBIGUOUS_ARGUMENT` error.
assert.throws(throwingSecond, 'Second');
// TypeError [ERR_AMBIGUOUS_ARGUMENT]

// The string is only used (as message) in case the function does not throw:
assert.throws(notThrowing, 'Second');
// AssertionError [ERR_ASSERTION]: Missing expected exception: Second

// If it was intended to match for the error message do this instead:
// It does not throw because the error messages match.
assert.throws(throwingSecond, /Second$/);

// If the error message does not match, an AssertionError is thrown.
assert.throws(throwingFirst, /Second$/);
// AssertionError [ERR_ASSERTION]const assert = require('node:assert/strict');

function throwingFirst() {
  throw new Error('First');
}

function throwingSecond() {
  throw new Error('Second');
}

function notThrowing() {}

// The second argument is a string and the input function threw an Error.
// The first case will not throw as it does not match for the error message
// thrown by the input function!
assert.throws(throwingFirst, 'Second');
// In the next example the message has no benefit over the message from the
// error and since it is not clear if the user intended to actually match
// against the error message, Node.js throws an `ERR_AMBIGUOUS_ARGUMENT` error.
assert.throws(throwingSecond, 'Second');
// TypeError [ERR_AMBIGUOUS_ARGUMENT]

// The string is only used (as message) in case the function does not throw:
assert.throws(notThrowing, 'Second');
// AssertionError [ERR_ASSERTION]: Missing expected exception: Second

// If it was intended to match for the error message do this instead:
// It does not throw because the error messages match.
assert.throws(throwingSecond, /Second$/);

// If the error message does not match, an AssertionError is thrown.
assert.throws(throwingFirst, /Second$/);
// AssertionError [ERR_ASSERTION]拷贝

由于符号容易混淆且容易出错，请避免将字符串作为第二个参数。

【Due to the confusing error-prone notation, avoid a string as the second argument.】