nodejs throw error

When developing in Node.js, we often use the throw statement to throw exceptions. When the program executes the throw statement, the program will stop execution and throw an exception. At this time, we can use the try...catch block to catch the exception and handle it.

However, when we use throw to report errors, sometimes some special situations may occur. This article will discuss these situations in detail and give corresponding solutions.

1. Throw string type error message

When using throw to report an error, we usually throw the error message in the form of a string, for example:

throw '未找到指定文件！';

However, in some cases, we may need to add some additional information when throwing an exception, such as the current time or the path to the executed file. At this point, we can use string templates to achieve:

throw `文件 ${filePath} 于 ${new Date()} 未找到！`;

By using template strings, you can easily splice strings, making the error message more detailed and useful.

2. Throw error information of Error object type

In addition to string type error information, we can also use Error objects to throw errors. This can make the error message more detailed, and can also add some other properties and methods to better handle errors.

For example:

throw new Error('未找到指定文件！', {
    code: 'ENOENT',
    path: '/usr/local/app'
});

In this example, we throw an Error object, which contains a string type error message and an object type property. This object contains some additional information, such as error code and execution file path, which can help us better handle errors.

3. Throw a custom error type

In some cases, we may need to use a custom error type to throw errors. For example, when developing an API, we may need to define some interface error types so that clients can better handle errors.

We can define our own error type by inheriting the Error class:

class APIError extends Error {
  constructor(message, code) {
    super(message);
    this.name = 'APIError';
    this.code = code;
  }
}

In this example, we define an APIError type inherited from the Error class and add an error message and an error code. When using it, we can throw a custom error type by throwing an error:

if (!user.hasPermission('ADMIN')) {
  throw new APIError('没有权限操作', 403);
}

In this way, our error message can be made clearer and easier to manage, and it can also communicate better with the client. to interact.

Summary

Using throw to report errors is a very common operation in Node.js. In actual development, we will encounter various situations and need to handle them accordingly. This article introduces methods of throwing string types, throwing Error object types, and throwing custom error types to help you better handle and manage errors.

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