Node.js Debugger Overview

Node.js provides built-in debugging capabilities that help developers identify and fix issues in their code. This summary outlines the essential features and usage of the Node.js debugger.

Key Concepts

• Debugger: A tool used to inspect the state of an application and control the execution flow.
• Breakpoints: Markers set in the code where the execution will pause, allowing developers to inspect variables and the call stack.
• Debugging Modes: Node.js can run in debugging mode, allowing for interactive debugging sessions.

Starting the Debugger

• To start a Node.js application in debug mode, use the command:

node inspect <filename>

Replace <filename> with your JavaScript file.

Debugging Commands

• Once in the debugger, you can use several commands to control the execution:
  • cont: Continue execution until the next breakpoint.
  • next: Step to the next line of code.
  • step: Step into functions.
  • out: Step out of the current function.
  • repl: Open a Read-Eval-Print Loop to evaluate expressions in the current context.

Setting Breakpoints

• You can set breakpoints directly in the code using the debugger; statement:

function test() {
    debugger; // Execution will pause here
    console.log("Debugging in progress");
}

test();

• Alternatively, you can set breakpoints using the debugger commands when in debug mode.

Additional Tools

• Chrome DevTools: Node.js can also be debugged using Chrome DevTools by starting your application with:

node --inspect <filename>

This opens up a debugging interface in your Chrome browser.

Conclusion

Using the built-in debugger in Node.js is essential for efficiently identifying and fixing bugs. By setting breakpoints and using debugger commands, you can gain insights into your application's execution flow and state.

For beginners, practicing with these debugging techniques will enhance your development skills and help you write more reliable code.