小程序中使用npm安装vant组件实现按需引入，减少代码包大小和避免触发用户隐私协议

npm install -g vant-tree-shaking

npm install -D vant-tree-shaking

{
  "name": "miniapp",
  "version": "1.0.0",
  "main": "app.js",
  "scripts": {
    "vant": "vant-tree-shaking",
  },
  "dependencies": {
    "@vant/weapp": "^1.11.5"
  },
  "devDependencies": {
    "vant-tree-shaking": "^1.0.0"
  }
}

// 1、扫描项目中的所有 json 文件，找出项目中使用到的所有 vant 组件
function readFile(filePath) {
  if (!filePath || !fs.existsSync(filePath)) return

  if (fs.statSync(filePath).isDirectory()) {
    let files = fs.readdirSync(filePath) || []
		files.map(m => {
      if (!IGNORE_DIRS.includes(m)) {
        let curPath = path.join(filePath, m)
        readFile(curPath)
      }
		})
  } else {
    getUsingComponents(filePath, vantSet)
  }
}

// 2、项目中使用到的 vant 组件依赖的其他 vant 组件
function readVantDir() {
  const files = fs.readdirSync(VANT_PATH) || []
  files.map(m => {
    if (!COMMON_DIRS.includes(m) && vantSet.has(`van-${m}`)) {
      const curPath = path.join(VANT_PATH, m, 'index.json')
      getUsingComponents(curPath, dependentSet)
    }
  })

  // 3、删除未使用到 vant 组件目录
  const usedVant = new Set([...vantSet, ...dependentSet])
  for (let i = files.length - 1; i >= 0; i--) {
    const cur = files[i]
    if (!COMMON_DIRS.includes(cur) && !usedVant.has(`van-${cur}`)) {
      const curPath = path.join(VANT_PATH, cur)
      deleteDir(curPath)
    }
  }
  console.log('vant-tree-shaking success')
}

/**
 * 读取 json 文件中的 usingComponents 属性值
 * @param {*} filePath 路径
 * @param {*} setList 存符合条件的 vant 组件名的列表
 */
function getUsingComponents(filePath, setList) {
  if (!filePath || !fs.existsSync(filePath) || !isJsonFile(filePath)) return

  try {
    const data = fs.readFileSync(filePath, 'utf8')
    const json = JSON.parse(data)
    const usingComponents = json.usingComponents || {}
    for (const key in usingComponents) {
      if (key.startsWith('van-')) {
        setList.add(key)
      }
    }
  } catch (err) {
    console.error(err)
  }
}