How to use debug in nodejs

Node.js is a very popular back-end programming language and is widely used to develop various web applications, servers, tools, frameworks and libraries. However, various problems will inevitably occur during the development process, such as code errors, logic errors, etc. At this time, a good debugging tool is very important. The debugging tool of Node.js is called debug, which can help developers quickly locate problems and solve them more efficiently.

This article will introduce how to use debug tools to debug code in Node.js.

1. Install the debug tool

Debug is a third-party library that can be installed and used through npm. Just execute the following command on the command line:

npm install debug

2. Use debug in the code

After the installation is completed, using debug in the code is very simple. You only need to add debug to the code that needs to be debugged. Introduce the debug library at the location:

const debug = require('debug')('myapp');

Among them, myapp is the namespace we defined for this code segment. This namespace can provide a unique prefix for your application to make it easier to distinguish and identify when debugging. they.

Next, in your code, you can use the debug log method to output debugging information:

debug('这是一条调试信息');

3. Enable debug information

By default, debug is Disabled. If you need to enable debugging, please set an environment variable named DEBUG when starting the Node.js process. For example, if you want to enable the debugging tool for myapp, you can execute the following command:

DEBUG=myapp node app.js

4. Use wildcards

If you have multiple namespaces in your application, you may want to enable them at the same time Their debug information. Wildcards are a very useful feature that allows you to enable debugging information for multiple namespaces in a more concise way. For example, if you want to enable debug information for all namespaces starting with myapp, you can execute the following command:

DEBUG=myapp:* node app.js

5. Use Visual Studio Code for debugging

In addition to using debug on the command line Tools, you can also use Visual Studio Code for debugging. Debugging Node.js applications in Visual Studio Code is very easy. First, open your code in Visual Studio Code, then in the debugging panel on the left, click the "Add Configuration" button.

Then, select "Node.js" as your debugging environment, and configure your startup script and parameters as follows:

{
    "type": "node",
    "request": "launch",
    "name": "Node.js",
    "program": "${workspaceFolder}/app.js",
    "cwd": "${workspaceFolder}",
    "runtimeExecutable": "node",
    "runtimeArgs": [
        "--inspect"
    ],
    "port": 9229
}

In this configuration, we used- The -inspect parameter starts the Node.js process and sets the debug port to 9229. After saving the configuration, you can click the "Start Debugging" button to start debugging.

6. Summary

Debug is a very powerful debugging tool that can help developers quickly locate and solve problems. Using debug is very simple. You only need to introduce the debug library into the code that needs to be debugged, and use its log method to output debugging information. To enable debug information, you need to set an environment variable named DEBUG. You can use wildcards to enable debug information for multiple namespaces at the same time. In addition to using debug on the command line, you can also use Visual Studio Code for debugging, which makes it easier to debug your code.

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