Debugger

Node’s debugger client doesn’t support the full range of commands, but
simple step and inspection is possible. By putting the statement debugger;
into the source code of your script, you will enable a breakpoint.

For example, suppose myscript.js looked like this:

The repl command allows you to evaluate code remotely. The next command
steps over to the next line. There are a few other commands available and more
to come. Type help to see others.

You can watch expression and variable values while debugging your code.
On every breakpoint each expression from the watchers list will be evaluated
in the current context and displayed just before the breakpoint’s source code
listing.

• cont, c - Continue execution
• step, s - Step in
• , o - Step out
• pause - Pause running code (like pause button in Developer Tools)

• setBreakpoint(), sb() - Set breakpoint on current line
• setBreakpoint(line), sb(line) - Set breakpoint on specific line
• setBreakpoint('fn()'), sb(...) - Set breakpoint on a first statement in
  functions body
• setBreakpoint('script.js', 1), sb(...) - Set breakpoint on first line of
  script.js
• clearBreakpoint, cb(...) - Clear breakpoint

It is also possible to set a breakpoint in a file (module) that
isn’t loaded yet:

• backtrace, bt - Print backtrace of current execution frame
• watch(expr) - Add expression to watch list
• unwatch(expr) - Remove expression from watch list
• watchers - List all watchers and their values (automatically listed on each
  breakpoint)
• repl - Open debugger’s repl for evaluation in debugging script’s context

• run - Run script (automatically runs on debugger’s start)
• restart - Restart script
• kill - Kill script

• scripts - List all loaded scripts
• version - Display v8’s version

The V8 debugger can be enabled and accessed either by starting Node with
the --debug command-line flag or by signaling an existing Node process
with SIGUSR1.

• - Connects to the process via the URI such as localhost:5858