__dirname,__filename,process.cwd(),path.resolve()区别

1.背景

目录结构是 test/a/b/foo.js, foo.js 里面的代码是:

const path = require("path");
console.log("__dirname:         " + __dirname);
console.log("__filename:        " + __filename);
console.log("process.cwd():     " + process.cwd());
console.log("path.resolve()     " + path.resolve());
console.log("path.resolve('')   " + path.resolve(""));
console.log("path.resolve('./') " + path.resolve("./"));

2.进入 test 目录

> cd ./test
> node ./a/b/foo.js

结果为:

• __dirname: /Users/zhengming/Desktop/test/a/b
• __filename: /Users/zhengming/Desktop/test/a/b/foo.js
• process.cwd(): /Users/zhengming/Desktop/test
• path.resolve(): /Users/zhengming/Desktop/test
• path.resolve(''): /Users/zhengming/Desktop/test
• path.resolve('./'): /Users/zhengming/Desktop/test

3.进入 test/a 目录执行命令

>cd ./test/a
>node ./b/foo.js

__dirname: /Users/zhengming/Desktop/test/a/b __filename: /Users/zhengming/Desktop/test/a/b/1.js process.cwd(): /Users/zhengming/Desktop/test/a path.resolve(): /Users/zhengming/Desktop/test/a path.resolve(''): /Users/zhengming/Desktop/test/a path.resolve('./'): /Users/zhengming/Desktop/test/a

4.修改 foo.js, 让它创建一个新的文件夹

结果 new-folder 目录的创建是在 **/test/目录下, 并不是在 /test/a/b 目录下

> node ./a/b/foo.js

// foo.js
const { access, mkdir } = require("fs").promises;

async function f() {
  const path = "./new-folder";
  try {
    await access(path);
  } catch (e) {
    await mkdir(path, { recursive: true });
  }
}
f();

5.总结

• __dirname: 返回被执行的 js 所在文件夹的绝对路径
• __filename: 返回被执行的 js 的绝对路径
• process.cwd(): 总是返回运行 node 命令时所在的文件夹的绝对路径
• path.resolve() 或 path.resolve('') 或 path.resolve('./'): 跟 process.cwd() 一样