# Node.js debugger
node --inspect-brk app.js
# Chrome DevTools: chrome://inspect

# Console debugging
console.log(JSON.stringify(obj, null, 2))
console.trace('Call stack here')
console.time('perf'); /* code */ console.timeEnd('perf')

# Memory leaks
node --expose-gc --max-old-space-size=4096 app.js

# Built-in debugger
python -m pdb script.py

# Breakpoint in code
breakpoint()  # Python 3.7+

# Verbose tracing
python -X tracemalloc script.py

# Profile
python -m cProfile -s cumulative script.py

# LLDB debugging
lldb ./MyApp
(lldb) breakpoint set --name main
(lldb) run
(lldb) po myVariable

# Xcode: Product → Profile (Instruments)

/* Outline all elements */
* { outline: 1px solid red !important; }

/* Debug specific element */
.debug { background: rgba(255,0,0,0.1) !important; }

# HTTP debugging
curl -v https://api.example.com/endpoint
curl -w "@curl-format.txt" -o /dev/null -s https://example.com

# DNS
dig example.com
nslookup example.com

# Ports
lsof -i :3000
netstat -tlnp

git bisect start
git bisect bad              # Current commit is broken
git bisect good abc1234     # Known good commit
# Git checks out middle commit — test it, then:
git bisect good  # or  git bisect bad
# Repeat until root cause commit is found
git bisect reset

# What's using this port?
lsof -i :PORT

# What's this process doing?
ps aux | grep PROCESS

# Watch file changes
fswatch -r ./src

# Disk space
df -h

# System resource usage
top -l 1 | head -10