debugger 调试器

$ node inspect myscript.js
< Debugger listening on ws://127.0.0.1:9229/80e7a814-7cd3-49fb-921a-2e02228cd5ba
< For help, see: https://nodejs.org/en/docs/inspector
< Debugger attached.
Break on start in myscript.js:1
> 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;
  2 setTimeout(() => {
  3   console.log('world');
debug>

Node.js 调试器客户端不是功能齐全的调试器，但可以进行简单的步骤和检查。

将语句 debugger; 插入脚本的源代码，则将在代码中的该位置启用断点：

// myscript.js
global.x = 5;
setTimeout(() => {
  debugger;
  console.log('world');
}, 1000);
console.log('hello');

一旦调试器运行，则断点将出现在第 3 行：

$ node inspect myscript.js
< Debugger listening on ws://127.0.0.1:9229/80e7a814-7cd3-49fb-921a-2e02228cd5ba
< For help, see: https://nodejs.org/en/docs/inspector
< Debugger attached.
Break on start in myscript.js:1
> 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;
  2 setTimeout(() => {
  3   debugger;
debug> cont
< hello
break in myscript.js:3
  1 (function (exports, require, module, __filename, __dirname) { global.x = 5;
  2 setTimeout(() => {
> 3   debugger;
  4   console.log('world');
  5 }, 1000);
debug> next
break in 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 myscript.js:5
  3   debugger;
  4   console.log('world');
> 5 }, 1000);
  6 console.log('hello');
  7
debug> .exit

repl 命令允许远程评估代码。 next 命令步进下一行。 键入 help 以查看可用的其他命令。

在不输入命令的情况下按 enter 将重复之前的调试器命令。

Node.js includes an out-of-process debugging utility accessible via a V8 Inspector and built-in debugging client. To use it, start Node.js with the inspect argument followed by the path to the script to debug; a prompt will be displayed indicating successful launch of the debugger:

$ node inspect myscript.js
< Debugger listening on ws://127.0.0.1:9229/80e7a814-7cd3-49fb-921a-2e02228cd5ba
< For help, see: https://nodejs.org/en/docs/inspector
< Debugger attached.
Break on start in myscript.js:1
> 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;
  2 setTimeout(() => {
  3   console.log('world');
debug>

The Node.js debugger client is not a full-featured debugger, 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:

// myscript.js
global.x = 5;
setTimeout(() => {
  debugger;
  console.log('world');
}, 1000);
console.log('hello');

Once the debugger is run, a breakpoint will occur at line 3:

$ node inspect myscript.js
< Debugger listening on ws://127.0.0.1:9229/80e7a814-7cd3-49fb-921a-2e02228cd5ba
< For help, see: https://nodejs.org/en/docs/inspector
< Debugger attached.
Break on start in myscript.js:1
> 1 (function (exports, require, module, __filename, __dirname) { global.x = 5;
  2 setTimeout(() => {
  3   debugger;
debug> cont
< hello
break in myscript.js:3
  1 (function (exports, require, module, __filename, __dirname) { global.x = 5;
  2 setTimeout(() => {
> 3   debugger;
  4   console.log('world');
  5 }, 1000);
debug> next
break in 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 myscript.js:5
  3   debugger;
  4   console.log('world');
> 5 }, 1000);
  6 console.log('hello');
  7
debug> .exit

The repl command allows code to be evaluated remotely. The next command steps to the next line. Type help to see what other commands are available.

Pressing enter without typing a command will repeat the previous debugger command.