JavaScript URL Decode — decodeURIComponent()

// 解码单个查询参数值——常见情况

const city     = decodeURIComponent('S%C3%A3o%20Paulo')          // 'São Paulo'
const district = decodeURIComponent('It%C3%A1im%20Bibi')         // 'Itáim Bibi'
const category = decodeURIComponent('office%20furniture')         // 'office furniture'
const filter   = decodeURIComponent('price%3A%5B200+TO+800%5D')  // 'price:[200+TO+800]'
// 注意：+ 不会被解码为空格——参见比较表中的 + 部分

console.log(city)      // São Paulo
console.log(district)  // Itáim Bibi
console.log(category)  // office furniture
console.log(filter)    // price:[200+TO+800]

// 重定向 URL 在嵌入为参数值时被百分号编码
// 接收端：提取它，然后使用它——使用 URLSearchParams 无需手动解码

const incomingUrl = 'https://auth.company.com/callback' +
  '?next=https%3A%2F%2Fdashboard.internal%2Freports%3Fview%3Dweekly%26team%3Dplatform' +
  '&session_id=sid_7x9p2k'

const url       = new URL(incomingUrl)
const rawNext   = url.searchParams.get('next')       // URLSearchParams 自动解码
const sessionId = url.searchParams.get('session_id') // 'sid_7x9p2k'

// rawNext 已经解码：'https://dashboard.internal/reports?view=weekly&team=platform'
// 不要再次调用 decodeURIComponent(rawNext)——那会是双重解码

const nextUrl = new URL(rawNext!)
console.log(nextUrl.hostname)                    // dashboard.internal
console.log(nextUrl.searchParams.get('view'))    // weekly
console.log(nextUrl.searchParams.get('team'))    // platform

// 包含国际化路径段的 REST API
// 原始字符的每个 UTF-8 字节分别被百分号编码

const encodedSegments = [
  '%E5%8C%97%E4%BA%AC',   // 北京 (Beijing)   — 每个字符 3 字节
  '%E6%B7%B1%E5%9C%B3',   // 深圳 (Shenzhen)  — 每个字符 3 字节
  'caf%C3%A9',            // café             — é 作为预组合 NFC
  'S%C3%A3o%20Paulo',     // São Paulo
]

encodedSegments.forEach(seg => {
  console.log(decodeURIComponent(seg))
})
// 北京
// 深圳
// café
// São Paulo

// 从存储 API URL 中提取文件键
// 对象键包含 / 因此在路径段内被编码为 %2F
const storageUrl = 'https://storage.api.example.com/v1/objects/reports%2F2025%2Fq1-financials.pdf'
const rawKey     = new URL(storageUrl).pathname.replace('/v1/objects/', '')
// .pathname 解码 URL 级别的编码，但 %2F（在 URL 级别为 %252F）保留
// 使用 decodeURIComponent 进行最后一步：
const fileKey = decodeURIComponent(rawKey)  // 'reports/2025/q1-financials.pdf'
console.log(fileKey)

// 包含国际化路径段和结构化查询字符串的 CDN URL
// decodeURI() 解码非 ASCII 路径，但保留 ? & = 完整

const encodedUrl =
  'https://cdn.example.com/assets/%E5%8C%97%E4%BA%AC%2F2025%2Fq1-report.pdf' +
  '?token=eyJ0eXAiOiJKV1QiLCJhbGci&expires=1735689600'

const readable = decodeURI(encodedUrl)
console.log(readable)
// https://cdn.example.com/assets/北京/2025/q1-report.pdf?token=eyJ0eXAiOiJKV1QiLCJhbGci&expires=1735689600
// ↑ 非 ASCII 已解码；? & = 已保留——URL 在结构上保持有效

// decodeURIComponent 会破坏 URL——: / ? & = 全部一次性解码
const broken = decodeURIComponent(encodedUrl)
// 在这里看起来相同，但像 'https%3A%2F%2F...' 这样的 URL 会被破坏

// 解析 webhook 回调或 OAuth 重定向查询字符串
const rawSearch =
  '?event_id=evt_9c2f4a1b' +
  '&product_name=Standing+Desk+Pro' +
  '&filter=price%3A%5B200+TO+800%5D' +
  '&tag=ergonomic&tag=adjustable' +
  '&redirect=https%3A%2F%2Fdashboard.internal%2Forders%3Fview%3Dpending'

const params = new URLSearchParams(rawSearch)

console.log(params.get('event_id'))      // 'evt_9c2f4a1b'
console.log(params.get('product_name'))  // 'Standing Desk Pro'       ← + 解码为空格
console.log(params.get('filter'))        // 'price:[200+TO+800]'      ← %3A 和 %5B 已解码
console.log(params.getAll('tag'))        // ['ergonomic', 'adjustable']
console.log(params.get('redirect'))      // 'https://dashboard.internal/orders?view=pending'

// 迭代所有参数
for (const [key, value] of params) {
  console.log(`${key}: ${value}`)
}
// event_id: evt_9c2f4a1b
// product_name: Standing Desk Pro
// filter: price:[200+TO+800]
// tag: ergonomic
// tag: adjustable
// redirect: https://dashboard.internal/orders?view=pending

// 当前 URL: https://app.example.com/search
//   ?q=standing+desk
//   &category=office+furniture
//   &sort=price_asc
//   &page=2

interface SearchFilters {
  query:    string | null
  category: string | null
  sort:     string
  page:     number
}

function getSearchFilters(): SearchFilters {
  const params = new URLSearchParams(window.location.search)
  return {
    query:    params.get('q'),                       // 'standing desk'
    category: params.get('category'),                // 'office furniture'
    sort:     params.get('sort') ?? 'relevance',
    page:     Number(params.get('page') ?? '1'),
  }
}

const filters = getSearchFilters()
console.log(filters.query)     // standing desk   (+ 自动解码)
console.log(filters.category)  // office furniture

import { createReadStream } from 'fs'
import { createInterface } from 'readline'

// 文件：orders-export.txt——每行一条 URL 编码记录
// customer_name=%E5%BC%A0%E4%BC%9F&order_id=ord_9c2f4a&product=Standing+Desk+Pro&total=149.99%20CNY
// customer_name=%E6%9D%8E%E5%A8%9C&order_id=ord_7b3a1c&product=Ergonomic+Chair&total=89.00%20CNY

interface Order {
  customerName: string | null
  orderId:      string | null
  product:      string | null
  total:        string | null
}

async function parseOrdersFile(filePath: string): Promise<Order[]> {
  const fileStream = createReadStream(filePath, { encoding: 'utf-8' })
  const rl         = createInterface({ input: fileStream, crlfDelay: Infinity })
  const orders: Order[] = []

  for await (const line of rl) {
    if (!line.trim()) continue

    // URLSearchParams 自动将 + 解码为空格并处理 %XX 序列
    const params = new URLSearchParams(line)

    orders.push({
      customerName: params.get('customer_name'),  // '张伟'
      orderId:      params.get('order_id'),        // 'ord_9c2f4a'
      product:      params.get('product'),         // 'Standing Desk Pro'
      total:        params.get('total'),           // '149.99 CNY'
    })
  }

  return orders
}

const orders = await parseOrdersFile('./orders-export.txt')
console.log(orders[0])
// { customerName: '张伟', orderId: 'ord_9c2f4a', product: 'Standing Desk Pro', total: '149.99 CNY' }

import { createReadStream } from 'fs'
import { createInterface } from 'readline'

// Nginx 访问日志行如下所示：
// 192.168.1.42 - - [11/Mar/2026:10:23:01 +0000] "GET /api/search?q=standing%20desk%26brand%3ANorthwood&sort=price_asc HTTP/1.1" 200 1842

async function extractSearchQueries(logFile: string): Promise<string[]> {
  const rl     = createInterface({ input: createReadStream(logFile), crlfDelay: Infinity })
  const queries: string[] = []

  for await (const line of rl) {
    // 从日志行中提取请求路径
    const match = line.match(/"GET ([^ ]+) HTTP/)
    if (!match) continue

    try {
      const requestUrl = new URL(match[1], 'http://localhost')
      const query      = requestUrl.searchParams.get('q')
      if (query) queries.push(query)  // URLSearchParams 自动解码
    } catch {
      // 跳过格式错误的行——访问日志可能包含截断的条目
    }
  }

  return queries
}

const queries = await extractSearchQueries('/var/log/nginx/access.log')
console.log(queries)
// ['standing desk&brand:Northwood', 'ergonomic chair', 'monitor arm 27 inch']

import http from 'http'

// 传入 URL: /api/products?q=standing+desk&warehouse=eu%2Dwest%2D1&minStock=10&cursor=eyJpZCI6MTIzfQ%3D%3D

const server = http.createServer((req, res) => {
  // 构造完整 URL——第二个参数是 URL 构造函数所需的基础地址
  const requestUrl = new URL(req.url!, 'http://localhost')

  const searchQuery = requestUrl.searchParams.get('q')            // 'standing desk'
  const warehouseId = requestUrl.searchParams.get('warehouse')    // 'eu-west-1'
  const minStock    = Number(requestUrl.searchParams.get('minStock') ?? '0')
  const cursor      = requestUrl.searchParams.get('cursor')       // 'eyJpZCI6MTIzfQ=='

  if (!warehouseId) {
    res.writeHead(400, { 'Content-Type': 'application/json' })
    res.end(JSON.stringify({ error: 'warehouse parameter is required' }))
    return
  }

  const cursorData = cursor ? JSON.parse(Buffer.from(cursor, 'base64').toString()) : null

  res.writeHead(200, { 'Content-Type': 'application/json' })
  res.end(JSON.stringify({ searchQuery, warehouseId, minStock, cursorData }))
})

server.listen(3000)

# ── Node.js 单行命令 ──────────────────────────────────────────────────

# 解码单个百分号编码值
node -e "console.log(decodeURIComponent(process.argv[1]))" "S%C3%A3o%20Paulo%20%26%20Rio"
# São Paulo & Rio

# 解析查询字符串并打印每个键=值对（已解码）
node -e "
  const params = new URLSearchParams(process.argv[1])
  for (const [k, v] of params) console.log(`${k} = ${v}`)
" "q=standing+desk&warehouse=eu%2Dwest%2D1&minStock=10"
# q = standing desk
# warehouse = eu-west-1
# minStock = 10

# 解码并美化打印 URL 编码的 JSON 体（webhook 调试中常见）
node -e "
  const raw = decodeURIComponent(process.argv[1])
  console.log(JSON.stringify(JSON.parse(raw), null, 2))
" '%7B%22event%22%3A%22purchase%22%2C%22amount%22%3A149.99%2C%22currency%22%3A%22CNY%22%7D'
# {
#   "event": "purchase",
#   "amount": 149.99,
#   "currency": "CNY"
# }

# ── Python 单行命令（在大多数 macOS/Linux 系统上可用）─────────────
# unquote_plus 也将 + 解码为空格——对于 form 编码数据是正确的
python3 -c "
from urllib.parse import unquote_plus
import sys
print(unquote_plus(sys.argv[1]))
" "Standing+Desk+%26+Ergonomic+Chair"
# Standing Desk & Ergonomic Chair

# ── curl——从响应头记录并解码重定向 URL ──────────
curl -sI "https://api.example.com/short/abc123" | grep -i location |   node -e "
    const line = require('fs').readFileSync('/dev/stdin', 'utf8')
    const url  = line.replace(/^location:s*/i, '').trim()
    console.log(decodeURIComponent(url))
  "

npm install decode-uri-component
# or
pnpm add decode-uri-component

import decodeUriComponent from 'decode-uri-component'

// 原生函数对格式错误的输入抛出异常——可能导致请求处理程序崩溃
try {
  decodeURIComponent('product%name%')   // ❌ URIError: URI malformed
} catch (e) {
  console.error('原生函数抛出：', (e as Error).message)
}

// decode-uri-component 返回原始序列而不是抛出
console.log(decodeUriComponent('product%name%'))
// product%name%   ← 格式错误的序列保持原样，不抛出异常

// 有效序列被正确解码
console.log(decodeUriComponent('S%C3%A3o%20Paulo%20%26%20Rio'))
// São Paulo & Rio

// 混合：有效序列被解码，无效序列被保留
console.log(decodeUriComponent('Beijing%20Office%20%ZZ%20HQ'))
// Beijing Office %ZZ HQ   ← %ZZ 不是有效的十六进制——保持原样

// 在日志处理流水线中的实际使用
const rawSearchQueries = [
  'standing%20desk%20ergonomic',
  'price%3A%5B200+TO+800%5D',
  '50%25+off',       // ← 使用 decodeURIComponent 会抛出（裸 %）
  'wireless%20keyboard%20%26%20mouse',
]

const decoded = rawSearchQueries.map(q => decodeUriComponent(q))
console.log(decoded)
// ['standing desk ergonomic', 'price:[200+TO+800]', '50%25+off', 'wireless keyboard & mouse']

// ── 1. 基本安全解码——出错时返回原始字符串 ─────────────
function safeDecode(encoded: string): string {
  try {
    return decodeURIComponent(encoded)
  } catch {
    return encoded  // 解码失败时返回原始输入——永不崩溃
  }
}

// ── 2. 安全解码 + 将 + 处理为空格（用于 form 编码值）───────
function safeFormDecode(formEncoded: string): string {
  try {
    return decodeURIComponent(formEncoded.replace(/+/g, ' '))
  } catch {
    return formEncoded.replace(/+/g, ' ')  // 即使其余失败也至少替换 +
  }
}

// ── 3. 安全的完整查询字符串解析器→普通对象 ─────────────────
function parseQueryString(queryString: string): Record<string, string> {
  const result: Record<string, string> = {}
  try {
    const params = new URLSearchParams(queryString)
    for (const [key, value] of params) {
      result[key] = value  // URLSearchParams 在内部处理所有解码
    }
  } catch {
    // 对完全格式错误的输入静默返回空对象
  }
  return result
}

// 使用
console.log(safeDecode('S%C3%A3o%20Paulo'))         // São Paulo
console.log(safeDecode('search%20for%2050%25+off'))  // search for 50% off（裸 %）
                                                     // → 实际上没问题；% 这里是 %25
console.log(safeDecode('malformed%string%'))         // malformed%string%（不抛出）

console.log(safeFormDecode('standing+desk+pro'))     // standing desk pro

console.log(parseQueryString('q=hello+world&tag=node%20js&page=2'))
// { q: 'hello world', tag: 'node js', page: '2' }