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An article to talk about the path module in node

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Release: 2022-12-14 20:04:15
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An article to talk about the path module in node

The path module is a built-in module in nodejs for processing file/directory paths. It can be regarded as a toolbox, providing many methods for us to use, of course they are all related to path processing. related. At the same time, the path module appears frequently in front-end development, such as when configuring webpack. This article introduces some commonly used methods in this module. Let’s learn together. [Related tutorial recommendations: nodejs video tutorial, Programming teaching]

  • It should be noted that all modules (built-in, custom) in nodejs are required Use requirer to import, generally the import position is at the top of the file.
const path = require('path');
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#API

basename (get the path base name)

  • path.basename(path [,ext])
    • path: file/directory path
    • ext: (optional) file extension such as .js .css, etc.
    • Return value: path path The last part
  • Note:
    • If path is not a string or the given ext parameter is not a string, a TypeError is thrown
    • If there is ext Parameter, when the ext suffix name matches the file name, the returned file name will omit the file suffix
    • If there is a directory separator at the end of the path, it will be ignored
const path = require("path");

path.basename('./ext/test.js') //test.js
path.basename('./ext/test.js','.js') //test (当后缀名与文件名匹配上时返回的文件名会省略文件后缀)
path.basename('./ext/test.js','.html') //test.js (没有匹配上时返回文件全名)
path.basename('./ext/foo/') // foo (尾部目录分隔符被忽略)
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dirname (get the path directory name)

  • path.dirname(path)
    • path: file/directory path
    • Return Value: path The directory name of the path
  • Note:
    • If path is not a string, a TypeError is thrown
    • If there is a directory separator at the end of path It will be ignored
const path = require("path");

path.dirname('./foo/bar/baz'); //./foo/bar (相对路径/绝对路径均可)
path.dirname('/foo/bar/baz/'); // /foo/bar (尾部目录分隔符被忽略)
path.dirname('/foo/bar/baz/test.js'); // /foo/bar/baz
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extname (get the path extension)

  • path.extname(path)
    • path: file/directory path
    • Return value: path extension, from the last occurrence of '.' character to the end of the string in the last part of path, if there is no extension, empty is returned
  • Note:
    • If path is not a string, a TypeError is thrown
const path = require("path");

path.extname('foo/bar/baz/test.js'); // .js
path.extname('foo/bar/baz');// '' (无扩展名返回 '')
path.extname('foo/bar/baz/.'); // ''
path.extname('foo/bar/baz/test.'); // '.'
path.extname('foo/bar/baz/.test'); // ''
path.extname('foo/bar/baz/.test.js'); // '.js'
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parse (parse path)

  • path.parse(path) ( str => obj )
    • path: file/directory path
    • Return value: with Object of attributes (dir, root, base, name, ext)
      • root: root directory
      • dir: folder where the file is located
      • base: complete file (index. js )
      • name: file name
      • ext: file suffix name
  • Note:
    • if If path is not a string, a TypeError will be thrown.
    • If there is a directory separator at the end, it will be ignored
  • A picture is worth a thousand words
┌──────────────────┬────────────┐
│          dir     │    base    │
├──────┬           ├──────┬─────┤
│ root │           │ name │ ext │
"  /    foo/bar/baz/ index  .js "
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const path = require("path");

path.parse('/foo/bar/baz/index.js')
// {
//     root: '/',
//     dir: '/foo/bar/baz',
//     base: 'index.js',
//     ext: '.js',
//     name: 'index'
//   }

path.parse('/foo/bar/baz') //尾部目录分隔符省略
// {
//     root: '/',
//     dir: '/foo/bar',
//     base: 'baz',
//     ext: '',
//     name: 'baz'
//   }

path.parse('./foo/bar/baz/index.js') //当路径为相对路径 ./ 或../时 解析结果中root(代表根目录,绝对路径才有值)为 ''
// {
//     root: '',
//     dir: './foo/bar/baz',
//     base: 'index.js',
//     ext: '.js',
//     name: 'index'
//   }
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format (serialization path)

  • path.format(pathObj) Serialization path path, just the opposite of path.parse()

    • pathObj: path object
    • Return value: serialized string path (obj => string)
  • Note:

    • If pathObject is not an object, a TypeError is thrown
    • The attributes in pathObject need to pay attention to the priority:
      • When the dir attribute exists, the root attribute is ignored
      • When the base attribute exists, the name and ext attributes will be ignored

##isAbsolute (whether it is an absolute path)

  • path.isAbsolute(path)

      path: file/directory path
    • Return value: true/false
  • Note:

      If path is not a string, a TypeError is thrown
    • If the given path string length is 0, false is returned
    Reference

    Detailed answers to front-end interview questions

const path = require("path");

path.isAbsolute('//foo'); // true
path.isAbsolute('\\\\foo'); // true
path.isAbsolute('C:/foo/..'); // true
path.isAbsolute('C:\\foo\\..'); // true
path.isAbsolute('./bar\\baz');  // false
path.isAbsolute('../bar/baz'); // false
path.isAbsolute('.'); // false
path.isAbsolute('');  // false
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join(拼接路径片段)

  • path.join([...paths])
    • paths:路径片段
    • 返回值:使用平台特定的分隔符作为定界符将所有给定的 path 片段连接在一起规范化后生成的路径
  • 注意:
    • 如果 paths 不是字符串片段,则抛出 TypeError
    • 零长度的 path 片段会被忽略
    • 如果连接后的路径字符长度为0,则返回 '.',表示当前工作目录
    • 目录分隔符有平台差异,windows 返回为 ' \ '
const path = require("path");

path.join('') // '.'
path.join('./') // '.\'path.join('../') // '..\'path.join('/foo/','bar','baz','../','index.js') // '\foo\bar\index.js'path.join('./bar','baz' ,'/','../','',index.js') // 'bar\index.js'
path.join('foo', {}, 'bar'); // 'TypeError: Path must be a string. Received {}'
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normalize(规范化路径)

  • path.normalize(path)
    • path: 文件/目录路径
    • 返回值:规范后的路径字符串
  • 注意:
    • 如果 path 不是字符串片段,则抛出 TypeError
    • 尾部的分隔符会保留
    • 如果 path字符串长度为0,则返回 '.',表示当前工作目录
    • 路径中的目录分隔符均会被替换成平台特定的目录分隔符,windows 系统 会将 '/' 或'' 均替换成 ''
    • 路径中连续的多个分隔符会被规范化为一个
    • 路径中最好不要出现单个 ' \ ',因为当和字母在一起的时候会被当做转义符
const path = require("path");

path.normalize('') // '.'path.normalize('temp//foo//bar//..//'); // temp\foo\path.normalize('C:////temp\\\\/\\/\\/foo/bar') // C:\temp\foo\barpath.normalize('..////foo//\bar/baz/') // ..\fooar\baz\ (转义字符出现)path.normalize('temp//foo/\bar') // temp\fooar (转义字符出现)
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relative(获取 from 到 to 的相对路径)

  • path.relative(from,to)
    • from,to: 文件/目录路径
    • 返回值:from 到 to 的相对路径(to 相对于 form 的相对路径)
  • 注意:
    • 如果 from 和 to 指向相同路径相同 则返回 ''
    • 如果 from 或 to 任何一方为空,则使用当前工作目录代替其空路径
const path = require("path");

//当前工作目录为 \Stone\node\node\path_module
path.relative('/foo/bar/baz','/foo/bar/dir/file.js') // ..\dir\file.js
path.relative('/foo/bar/baz','/foo/bar/baz') // ''
path.relative('/foo/bar/baz/files.js','') // ..\..\..\..\Stone\node\node\path_module
path.relative('','/foo/bar/baz/files.js') // ..\..\..\..\foo\bar\baz\files.js
path.relative('','./foo/bar/baz/files.js') // foo\bar\baz\files.js
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这里针对 from 或 to 任何一方为空,则使用当前工作目录代替其空路径。稍作说明下, 例如当前工作目录为 \Stone\node\node\path_module,则可以看到 path.relative('/foo/bar/baz/files.js','') 的输出结果为..\..\..\..\Stone\node\node\path_module,此时 to 为 \Stone\node\node\path_module, 要输出 to 相对于 from 的相对路径,则 from 需要先 ../ 的形式 一层一层退出,来检索与 to 的公共父级目录,直到遇到公共父级目录或者到根目录停止,然后cd 进 to 目录。这是针对另一方为绝对路径,如果另一方为相对路径,则直接就是当前另一方路径。

resolve(将路径或路径片段的序列解析为绝对路径)

  • path.resolve([...paths])
    • paths: 路径或路径片段的序列
    • 返回值:路径或路径片段序列解析为绝对路径。(将路径片段解析后生成的绝对路径)
  • 注意:
    • 路径片段如果给出则必须是字符串类型,否则类型错误
    • 给定的路径序列从右到左进行处理,每个后续的 path 前置,直到构造出一个绝对路径
    • 如果处理完所有给定的 path 片段之后还未生成绝对路径,则再加上当前工作目录
    • 生成的路径均已规范化,并且除非将路径解析为根目录,否则将删除尾部斜杠
    • 零长度的 path 片段会被忽略
    • 若没有传入 path 片段,则 path.resolve() 将返回当前工作目录的绝对路径
const path = require("path");

//当前工作目录为 \Stone\node\node\path_module
path.resolve('/foo/bar', './baz'); // '/foo/bar/baz'
path.resolve('/foo/bar','', '/tmp/file/'); //'/tmp/file'
path.resolve('root', 'foo/baz/', '../fun/bar') // '\Stone\node\node\path_module\root\foo\fun\bar'
path.resolve() // '\Stone\node\node\path_module'
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path.resolve 方法解析路径片段的时候会从右往左的顺序依次解析,直到构造出一个绝对路径,否则会将当前工作目录加在路径开头。所以,通过 resolve 解析生成的路径一定是绝对路径。这个方法使用的非常多,应该特眼熟,对,前端我们配置 webpack 的时候会高频率用到,并且往往还会结合 __dirname 使用。

__dirname,__filename

  • __dirname:可以看作是 nodejs 中的全局变量,它始终表示当前执行文件所在目录的完整目录名(绝对路径)
  • __filename:可以看作是 nodejs 中的全局变量,它始终表示当前执行文件的完整文件名(完整绝对路)

我们先在 path_module 目录下运行 node test.js 命令

<!--当前执行文件的完整路径为\Stone\node\node\path_module\test.js-->
const path = require("path");

console.log(__dirname); // \Stone\node\node\path_module
console.log(__filename); // \Stone\node\node\path_module\test.js
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然后我们在 \Stone\node\node 目录下运行 node path_module\test.js,会发现输出结果同上, 所以这就是说明 __dirname 和 __filename 始终跟当前执行文件有关,跟启动脚本所在目录无关。

./ ../

./../ 我们都知道是相对路径的写法,但是使用的过程中配合 require() 使用与否的结果是不同的。

  • fs_module 目录下 执行 node test.js
<!--当前启动脚本的执行命令所在目录 \Stone\node\node\fs_module\test.js-->
const fs = require(&#39;fs&#39;)

fs.readFileSync(&#39;./ext/test1.js&#39;,(err,data)=> {
    console.log(&#39;ok&#39;)
})
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会正常打印出 ok

  • \Stone\node\node 目录下 执行 node fs_module\test.js
<!--当前启动脚本的执行命令所在目录 \Stone\node\node-->
const fs = require(&#39;fs&#39;)

fs.readFile(&#39;./ext/test1.js&#39;,(err,data)=> {
    console.log(&#39;ok&#39;)
})
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运行会报错 no such file or directory, open './ext/test1.js'

这到底是为啥嘞,原因就是 './' 和 '../' 的路径表示意义需要分情况,当结合 require() 使用的时候相对于当前执行文件,如果不结合 require() 使用的情况下会相对于当前启动脚本的目录,因此只有在 require() 时才使用相对路径(./, ../) 的写法,其他地方一律使用绝对路径,这点一定要注意。

结语

关于nodejs path 模块,我们今天就说到这里了,虽然 api 不是很多,但是 path 模块在前端的使用频率还是非常高的,所以觉得很值得学习了解一下的。由于认知有限,本文若有不准确之处还望路过的各位兄台及时指正,吃瓜,吃瓜。

更多node相关知识,请访问:nodejs 教程

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