How do I debug Node.js applications?

Question

How do I debug a Node.js server application?

Right now I\'m mostly using alert debugging with print statements like this:

sys.puts(sys.inspe         


        

Answer 1

Assuming you have node-inspector installed on your computer (if not, just type 'npm install -g node-inspector') you just have to run:

node-inspector & node --debug-brk scriptFileName.js

And paste the URI from the command line into a WebKit (Chrome / Safari) browser.

Answer 2

The V8 debugger released as part of the Google Chrome Developer Tools can be used to debug Node.js scripts. A detailed explanation of how this works can be found in the Node.js GitHub wiki.

Answer 3

There is built-in command line debugger client within Node.js. Cloud 9 IDE have also pretty nice (visual) debugger.

Answer 4

There are many possibilities...

• node includes a debugging utility
• node-inspector
• Code editors / IDEs (see debug instructions for one of the following)
  • Atom,
  • VSCode
  • Webstorm
  • and more

Debug support is often implemented using the v8 Debugging Protocol or the newer Chrome Debugging Protocol.

Answer 5

Debugging

• Joyent's Guide
• Debugger
• Node Inspector
• Visual Studio Code
• Cloud9
• Brackets

Profiling

1. node --prof ./app.js
2. node --prof-process ./the-generated-log-file

Heapdumps

• node-heapdump with Chrome Developer Tools

Flamegraphs

• 0x
• jam3/devtool then Chrome Developer Tools Flame Charts
• Dtrace and StackVis — Only supported on SmartOS
• clinicjs

Tracing

• Interactive Stack Traces with TraceGL

Logging

Libraries that output debugging information

• Caterpillar
• Tracer
• scribbles

Libraries that enhance stack trace information

• Longjohn

Benchmarking

• Apache Bench: ab -n 100000 -c 1 http://127.0.0.1:9778/
• wrk

Other

• Trace
• Vantage
• Bugger
• Google Tracing Framework
• Paul Irish's Guide

Legacy

These use to work but are no longer maintained or no longer applicable to modern node versions.

• https://github.com/bnoordhuis/node-profiler - replaced by built-in debugging
• https://github.com/c4milo/node-webkit-agent - replaced by node inspector
• https://nodetime.com/ - defunct

Answer 6

Theseus is a project by Adobe research which lets you debug your Node.js code in their Open Source editor Brackets. It has some interesting features like real-time code coverage, retroactive inspection, asynchronous call tree.