javascript - 这是 Node/promisify 异步函数的有效语法吗？

Question

我不小心输入了 await(await stat(content...) 并且它起作用了。不确定这是否是有效的语法，或者有更好的方法吗？我正在尝试阅读所有属于目录且与我的正则表达式不匹配的文件。

const fs = require('fs')
const path = require('path')
const content = path.resolve('.') + '/docs' + '/'
const util = require('util');
const stat = util.promisify(fs.stat)
const readDir = util.promisify(fs.readdir)
const directories = 'docs/';
const exclude = new RegExp(/^(adir|\.somedir)/,'i');
let newFiles = {}

async function main(){
    const ls = await readDir(directories)
    console.log('starting....');
    let newArray = []
     for (let index = 0; index < ls.length; index++) {
               let x =  await (await stat(content + ls[index])).isDirectory()
               let file = ls[index]
               if (x && !(exclude.test(file))){newArray.push(file)}
               console.log('x is ',x);
        }   
    console.log('new filtered array: ', newArray);
}

Answer 1

ls

我的建议是不要把所有鸡蛋放在一个篮子里。我们可以使用 Node 的 fs.Dirent 编写一个超快的 ls 函数。对象并绕过对每个文件进行缓慢的 fs.stat 调用的需要 -

// fsext.js

import { readdir } from "fs/promises"
import { join } from "path"

async function* ls (path = ".")
{ yield { dir: path }
  for (const dirent of await readdir(path, { withFileTypes: true }))
    if (dirent.isDirectory())
      yield *ls(join(path, dirent.name))
    else
      yield { file: join(path, dirent.name) }
}

async function toArray (iter)
{ const r = []
  for await (const v of iter)
    r.push(v)
  return r
}

export { ls, toArray }

// main.js

import { ls, toArray } from "./fsext.js"

toArray(ls("./node_modules")).then(console.log, console.error)

为了测试它，让我们添加一些流行的 npm 包，这样我们就有一个大的层次结构来测试我们的程序。我们将安装该批处理并计算目录和文件的数量 -

$ npm install async chalk commander debug express immutable lodash moment prop-types react react-dom request webpack

$ find ./node_modules | wc -l

5453

现在让我们运行我们的程序并对其进行计时 -

$ time node main.js

[
  { dir: './node_modules' },
  { dir: 'node_modules/.bin' },
  { file: 'node_modules/.bin/acorn' },
  { file: 'node_modules/.bin/browserslist' },
  { file: 'node_modules/.bin/loose-envify' },
  { file: 'node_modules/.bin/mime' },
  { file: 'node_modules/.bin/sshpk-conv' },
  { file: 'node_modules/.bin/sshpk-sign' },
  { file: 'node_modules/.bin/sshpk-verify' },
  { file: 'node_modules/.bin/terser' },
  { file: 'node_modules/.bin/uuid' },
  { file: 'node_modules/.bin/webpack' },
  { file: 'node_modules/.package-lock.json' },
  { dir: 'node_modules/@types' },
  { dir: 'node_modules/@types/eslint' },
  { file: 'node_modules/@types/eslint/LICENSE' },
  { file: 'node_modules/@types/eslint/README.md' },
  { file: 'node_modules/@types/eslint/helpers.d.ts' },
  { file: 'node_modules/@types/eslint/index.d.ts' },
  { dir: 'node_modules/@types/eslint/lib' },
   ... 5433 more items
]

node main.js  0.09s user 0.02s system 116% cpu 0.099 total

目录

如果我们只需要目录，我们可以将 dirs 编写为通用 ls 的简单特化 -

// fsext.js (continued)

async function* dirs (path)
{ for await (const f of ls(path))
    if (f.dir)
      yield f.dir
}

$ find ./node_modules -type d | wc -l

457

现在将其与我们的程序进行比较

// main.js

import { dirs, toArray } from "./fsext.js"

toArray(dirs("./node_modules")).then(console.log, console.error)

$ time node.main.js

[
  './node_modules',
  'node_modules/.bin',
  'node_modules/@types',
  'node_modules/@types/eslint',
  'node_modules/@types/eslint/lib',
  'node_modules/@types/eslint/lib/rules',
  'node_modules/@types/eslint/rules',
  'node_modules/@types/eslint-scope',
  'node_modules/@types/estree',
  'node_modules/@types/json-schema',
  'node_modules/@types/node',
  'node_modules/@types/node/assert',
  'node_modules/@types/node/dns',
  'node_modules/@types/node/fs',
  'node_modules/@types/node/stream',
  'node_modules/@types/node/timers',
  'node_modules/@types/node/ts3.6',
  'node_modules/@webassemblyjs',
  'node_modules/@webassemblyjs/ast',
  'node_modules/@webassemblyjs/ast/esm',
  ... 437 more items
]

node main2.js  0.09s user 0.02s system 108% cpu 0.099 total

排除

如果我们想排除某些目录或文件，我们也可以通用地编写它 -

// fsext.js (continued)

async function* exclude (iter, test)
{ for await (const v of iter)
    if (Boolean(test(v)))
      continue
    else
      yield v
}

// main.js

import { dirs, exclude, toArray } from "./fsext.js"

toArray(exclude(dirs("./node_modules"), v => /@/.test(v)))
  .then(console.log, console.error)

$ time node main.js

[
  './node_modules',
  'node_modules/.bin',
  'node_modules/accepts',
  'node_modules/acorn',
  'node_modules/acorn/bin',
  'node_modules/acorn/dist',
  'node_modules/ajv',
  'node_modules/ajv/dist',
  'node_modules/ajv/lib',
  'node_modules/ajv/lib/compile',
  'node_modules/ajv/lib/dot',
  'node_modules/ajv/lib/dotjs',
  'node_modules/ajv/lib/refs',
  'node_modules/ajv/scripts',
  'node_modules/ajv-keywords',
  'node_modules/ajv-keywords/keywords',
  'node_modules/ajv-keywords/keywords/dot',
  'node_modules/ajv-keywords/keywords/dotjs',
  'node_modules/ansi-styles',
  'node_modules/array-flatten',
  ... 351 more items
]

node main.js  0.09s user 0.02s system 105% cpu 0.104 total

重组

在我们的文件系统扩展模块 fsext 中，我们编写了两个适用于任何可迭代对象的函数，而不仅仅是 ls 或 >目录。我建议将它们分解成自己的 iter 模块。这种类型的重组有助于解耦问题并最大限度地提高整个程序中的代码重用 -

// iter.js

async function* empty () {}

async function* exclude (iter = empty(), test = Boolean)
{ for await (const v of iter)
    if (Boolean(test(v)))
      continue
    else
      yield v
}

async function toArray (iter = empty())
{ const r = []
  for await (const v of iter)
    r.push(v)
  return r
}

export { empty, exclude, toArray }

// fsext.js

import { readdir } from "fs/promises"
import { join } from "path"

async function* ls (path = ".")
{ yield { dir: path }
  for (const dirent of await readdir(path, { withFileTypes: true }))
    if (dirent.isDirectory())
      yield *ls(join(path, dirent.name))
    else
      yield { file: join(path, dirent.name) }
}

async function* dirs (path)
{ for await (const f of ls(path))
    if (f.dir)
      yield f.dir
}

async function* files (path)
{ for await (const f of ls(path))
    if (f.file)
      yield f.file
}

export { ls, dirs, files }

// main.js

import { dirs } from "./fsext.js"
import { exclude, toArray } from "./iter.js"

const somePath = "..."
const someTest = v => ...

toArray(exclude(dirs(somePath), someTest))
  .then(console.log, console.error)

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