mirror of
https://github.com/nodejs/node.git
synced 2025-05-15 08:02:06 +00:00
334a7e3614
This commit replaces multiple usages of `function(){}` with ES2015
arrow functions in places it was forgotten earlier. The goal is to
make the docs more consistent since other functions were already
replaced with ES2015 arrows.
In addition, it fixes invalid syntax in modules.markdown to valid
syntax as well as remove `var self = this` pattern usages in the code
where they are now possible to avoid through arrow functions.
PR-URL: https://github.com/nodejs/node/pull/4832
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
183 lines
4.9 KiB
Markdown
183 lines
4.9 KiB
Markdown
# Debugger
|
|
|
|
Stability: 2 - Stable
|
|
|
|
<!-- type=misc -->
|
|
|
|
Node.js includes a full-featured out-of-process debugging utility accessible
|
|
via a simple [TCP-based protocol][] and built-in debugging client. To use it,
|
|
start Node.js with the `debug` argument followed by the path to the script to
|
|
debug; a prompt will be displayed indicating successful launch of the debugger:
|
|
|
|
```
|
|
$ node debug myscript.js
|
|
< debugger listening on port 5858
|
|
connecting... ok
|
|
break in /home/indutny/Code/git/indutny/myscript.js:1
|
|
1 x = 5;
|
|
2 setTimeout(() => {
|
|
3 debugger;
|
|
debug>
|
|
```
|
|
|
|
Node.js's debugger client does not yet support the full range of commands, but
|
|
simple step and inspection are possible.
|
|
|
|
Inserting the statement `debugger;` into the source code of a script will
|
|
enable a breakpoint at that position in the code.
|
|
|
|
For example, suppose `myscript.js` is written as:
|
|
|
|
```js
|
|
// myscript.js
|
|
x = 5;
|
|
setTimeout(() => {
|
|
debugger;
|
|
console.log('world');
|
|
}, 1000);
|
|
console.log('hello');
|
|
```
|
|
|
|
Once the debugger is run, a breakpoint will occur at line 4:
|
|
|
|
```
|
|
$ node debug myscript.js
|
|
< debugger listening on port 5858
|
|
connecting... ok
|
|
break in /home/indutny/Code/git/indutny/myscript.js:1
|
|
1 x = 5;
|
|
2 setTimeout(() => {
|
|
3 debugger;
|
|
debug> cont
|
|
< hello
|
|
break in /home/indutny/Code/git/indutny/myscript.js:3
|
|
1 x = 5;
|
|
2 setTimeout(() => {
|
|
3 debugger;
|
|
4 console.log('world');
|
|
5 }, 1000);
|
|
debug> next
|
|
break in /home/indutny/Code/git/indutny/myscript.js:4
|
|
2 setTimeout(() => {
|
|
3 debugger;
|
|
4 console.log('world');
|
|
5 }, 1000);
|
|
6 console.log('hello');
|
|
debug> repl
|
|
Press Ctrl + C to leave debug repl
|
|
> x
|
|
5
|
|
> 2+2
|
|
4
|
|
debug> next
|
|
< world
|
|
break in /home/indutny/Code/git/indutny/myscript.js:5
|
|
3 debugger;
|
|
4 console.log('world');
|
|
5 }, 1000);
|
|
6 console.log('hello');
|
|
7
|
|
debug> quit
|
|
```
|
|
|
|
The `repl` command allows code to be evaluated remotely. The `next` command
|
|
steps over to the next line. Type `help` to see what other commands are
|
|
available.
|
|
|
|
## Watchers
|
|
|
|
It is possible to watch expression and variable values while debugging. On
|
|
every breakpoint, each expression from the watchers list will be evaluated
|
|
in the current context and displayed immediately before the breakpoint's
|
|
source code listing.
|
|
|
|
To begin watching an expression, type `watch('my_expression')`. The command
|
|
`watchers` will print the active watchers. To remove a watcher, type
|
|
`unwatch('my_expression')`.
|
|
|
|
## Commands reference
|
|
|
|
### Stepping
|
|
|
|
* `cont`, `c` - Continue execution
|
|
* `next`, `n` - Step next
|
|
* `step`, `s` - Step in
|
|
* `out`, `o` - Step out
|
|
* `pause` - Pause running code (like pause button in Developer Tools)
|
|
|
|
### Breakpoints
|
|
|
|
* `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('script.js', 1)`, `cb(...)` - Clear breakpoint in script.js
|
|
on line 1
|
|
|
|
It is also possible to set a breakpoint in a file (module) that
|
|
isn't loaded yet:
|
|
|
|
```
|
|
$ ./node debug test/fixtures/break-in-module/main.js
|
|
< debugger listening on port 5858
|
|
connecting to port 5858... ok
|
|
break in test/fixtures/break-in-module/main.js:1
|
|
1 var mod = require('./mod.js');
|
|
2 mod.hello();
|
|
3 mod.hello();
|
|
debug> setBreakpoint('mod.js', 23)
|
|
Warning: script 'mod.js' was not loaded yet.
|
|
1 var mod = require('./mod.js');
|
|
2 mod.hello();
|
|
3 mod.hello();
|
|
debug> c
|
|
break in test/fixtures/break-in-module/mod.js:23
|
|
21
|
|
22 exports.hello = () => {
|
|
23 return 'hello from module';
|
|
24 };
|
|
25
|
|
debug>
|
|
```
|
|
|
|
### Info
|
|
|
|
* `backtrace`, `bt` - Print backtrace of current execution frame
|
|
* `list(5)` - List scripts source code with 5 line context (5 lines before and
|
|
after)
|
|
* `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
|
|
* `exec expr` - Execute an expression in debugging script's context
|
|
|
|
### Execution control
|
|
|
|
* `run` - Run script (automatically runs on debugger's start)
|
|
* `restart` - Restart script
|
|
* `kill` - Kill script
|
|
|
|
### Various
|
|
|
|
* `scripts` - List all loaded scripts
|
|
* `version` - Display V8's version
|
|
|
|
## Advanced Usage
|
|
|
|
An alternative way of enabling and accessing the debugger is to start
|
|
Node.js with the `--debug` command-line flag or by signaling an existing
|
|
Node.js process with `SIGUSR1`.
|
|
|
|
Once a process has been set in debug mode this way, it can be connected to
|
|
using the Node.js debugger by either connecting to the `pid` of the running
|
|
process or via URI reference to the listening debugger:
|
|
|
|
* `node debug -p <pid>` - Connects to the process via the `pid`
|
|
* `node debug <URI>` - Connects to the process via the URI such as
|
|
localhost:5858
|
|
|
|
[TCP-based protocol]: https://github.com/v8/v8/wiki/Debugging-Protocol
|