How to debug nodejs

Node.js is a Javascript running environment based on the Chrome V8 JavaScript engine. It is a lightweight, efficient, scalable platform for building web-based applications and server-side applications.

However, although Node.js is powerful, we may also encounter some problems when we are developing applications. In this case, we need to understand how to debug Node.js. Debugging Node.js helps us identify bugs and issues in our application and fix them. In this article, we will learn how to debug Node.js.

1. Use debugger statements

Inserting debugger statements into the application can help us pause the execution of the code and view variables and execution paths in the console. For example:

function sum(a, b) {
  debugger;
  return a + b;
}

When the code is executed to the debugger statement, it will automatically pause. At this point, you can execute the command in the console and view the variables.

2. Use the built-in debugger of Node.js

Node.js has a built-in debugger that we can use for debugging. To use the debugger for Node.js, enter the following command in the terminal:

node debug app.js

where app.js is the file name of the application you want to debug. In the debugger, you can use the following commands:

• c: Continue executing code
• n: Execute next line of code
• s: Enter the current function
• o: Jump out of the current function
• repl: In the current context Opening the REPL

in the console allows you to view variable values ​​and the call stack.

3. Use the debugging tools of Node.js

In addition to the built-in debugger, Node.js also has many debugging tools available. One of the most popular tools is Node Inspector. Node Inspector is a web-based debugger that allows you to debug Node.js applications in a web browser.

To use Node Inspector, first install it:

npm install -g node-inspector

Then, enter the following command in the terminal:

node-inspector &

This will open a new window in your browser . To start debugging a Node.js application, enter the following command in the terminal:

node --debug app.js

where app.js is the file name of the application you want to debug. Next, visit http://localhost:8080/debug?port=5858 in your browser. This will open a debugger.

In the debugger, you can set breakpoints, view variable values, and the call stack.

4. Use third-party tools

In addition to Node Inspector, there are many third-party debugging tools available. Some of these tools include:

• WebStorm: WebStorm is a web-based integrated development environment (IDE) that supports Node.js’ built-in debugger.
• Visual Studio Code: Visual Studio Code is a free cross-platform code editor that supports debugging and integrated breakpoints in Node.js code.
• Chrome DevTools: Chrome DevTools is a powerful tool for debugging Node.js in a web browser. To use Chrome DevTools, enter the following command in the terminal:

node --inspect app.js

where app.js is the file name of the application you want to debug. Next, open chrome://inspect in Chrome browser and you will see a link related to Node.js application. Click the "inspect" button to open Chrome DevTools.

In short, how to debug Node.js depends on personal preference and development environment. You can choose to use the built-in debugger, a third-party debugger, or some other tool to debug your application. No matter which tool you choose, debugging Node.js is essential to help us find and fix problems in our application.

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