调试器

【Debugger】

Node.js 包含一个命令行调试工具。Node.js 调试器客户端并不是一个功能齐全的调试器，但可以进行简单的逐步执行和检查。

【Node.js includes a command-line debugging utility. The Node.js debugger client is not a full-featured debugger, but simple stepping and inspection are possible.】

要使用它，请使用 inspect 参数启动 Node.js，然后跟上要调试的脚本路径。

【To use it, start Node.js with the inspect argument followed by the path to the script to debug.】

$ node inspect myscript.js
< Debugger listening on ws://127.0.0.1:9229/621111f9-ffcb-4e82-b718-48a145fa5db8
< For help, see: https://nodejs.cn/docs/inspector
<
connecting to 127.0.0.1:9229 ... ok
< Debugger attached.
<
 ok
Break on start in myscript.js:2
  1 // myscript.js
> 2 global.x = 5;
  3 setTimeout(() => {
  4   debugger;
debug> 拷贝

调试器会自动在第一个可执行行处中断。若希望运行到第一个断点（由 debugger 语句指定），请将环境变量 NODE_INSPECT_RESUME_ON_START 设置为 1。

【The debugger automatically breaks on the first executable line. To instead run until the first breakpoint (specified by a debugger statement), set the NODE_INSPECT_RESUME_ON_START environment variable to 1.】

$ cat myscript.js
// myscript.js
global.x = 5;
setTimeout(() => {
  debugger;
  console.log('world');
}, 1000);
console.log('hello');
$ NODE_INSPECT_RESUME_ON_START=1 node inspect myscript.js
< Debugger listening on ws://127.0.0.1:9229/f1ed133e-7876-495b-83ae-c32c6fc319c2
< For help, see: https://nodejs.cn/docs/inspector
<
connecting to 127.0.0.1:9229 ... ok
< Debugger attached.
<
< hello
<
break in myscript.js:4
  2 global.x = 5;
  3 setTimeout(() => {
> 4   debugger;
  5   console.log('world');
  6 }, 1000);
debug> next
break in myscript.js:5
  3 setTimeout(() => {
  4   debugger;
> 5   console.log('world');
  6 }, 1000);
  7 console.log('hello');
debug> repl
Press Ctrl+C to leave debug repl
> x
5
> 2 + 2
4
debug> next
< world
<
break in myscript.js:6
  4   debugger;
  5   console.log('world');
> 6 }, 1000);
  7 console.log('hello');
  8
debug> .exit
$ 拷贝

repl 命令允许远程评估代码。next 命令会执行到下一行。输入 help 查看其他可用命令。

【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.】

在未输入命令而按下 enter 时，将会重复上一条调试命令。

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