text: const fs = require("fs");
  const path = require("path");
  const paths = require("./paths");
  // 保证paths.js文件在env.js之后被载入，并且可读取.env的环境变量
  delete require.cache[require.resolve("./paths")];
  
  const NODE_ENV = process.env.NODE_ENV;
  if (!NODE_ENV) {
      throw new Error(
          "[Zero] The NODE_ENV environment variable is required but was not specified."
      );
  }
  const dotenvFiles = [
      `${paths.dotenv}.${NODE_ENV}.local`,
      `${paths.dotenv}.${NODE_ENV}`,
      // Don't include `.env.local` for `test` environment
      // since normally you expect tests to produce the same
      // results for everyone
      NODE_ENV !== "test" && `${paths.dotenv}.local`,
      paths.dotenv
  ].filter(Boolean);
  
  // Load environment variables from .env* files. Suppress warnings using silent
  // if this file is missing. dotenv will never modify any environment variables
  // that have already been set.
  // https://github.com/motdotla/dotenv
  dotenvFiles.forEach(dotenvFile => {
      if (fs.existsSync(dotenvFile)) {
          require("dotenv").config({
              path: dotenvFile
          });
      }
  });
  
  // We support resolving modules according to `NODE_PATH`.
  // This lets you use absolute paths in imports inside large monorepos:
  // https://github.com/facebookincubator/create-react-app/issues/253.
  // It works similar to `NODE_PATH` in Node itself:
  // https://nodejs.org/api/modules.html#modules_loading_from_the_global_folders
  // Note that unlike in Node, only *relative* paths from `NODE_PATH` are honored.
  // Otherwise, we risk importing Node.js core modules into an app instead of Webpack shims.
  // https://github.com/facebookincubator/create-react-app/issues/1023#issuecomment-265344421
  // We also resolve them to make sure all tools using them work consistently.
  const appDirectory = fs.realpathSync(process.cwd());
  process.env.NODE_PATH = (process.env.NODE_PATH || "")
      .split(path.delimiter)
      .filter(folder => folder && !path.isAbsolute(folder))
      .map(folder => path.resolve(appDirectory, folder))
      .join(path.delimiter);
  
  // Grab NODE_ENV and REACT_APP_* environment variables and prepare them to be
  // injected into the application via DefinePlugin in Webpack configuration.
  const REACT_APP = /^REACT_APP_/i;
  
  function getClientEnvironment(publicUrl) {
      // 运行时才操作的环境变量
      function getEnv() {
          const zEnvs = {};
          for (const eKey in process.env) {
              if (process.env.hasOwnProperty(eKey)) {
                  if (eKey.startsWith("Z_")) {
                      const key = `${eKey.substring(2)}`;
                      zEnvs[key] = process.env[eKey];
                  }
              }
          }
          return zEnvs;
      }
  
      const envs = getEnv();
      // Z_专用环境变量处理a
      const raw = Object.keys(process.env)
          .filter(key => REACT_APP.test(key))
          .reduce(
              (env, key) => {
                  env[key] = process.env[key];
                  return env;
              },
              {
                  // Useful for determining whether we’re running in production mode.
                  // Most importantly, it switches React into the correct mode.
                  NODE_ENV: process.env.NODE_ENV || "development",
                  BABEL_ENV: process.env.NODE_ENV || "development",
                  // Useful for resolving the correct path to static assets in `public`.
                  // For example, <img src={process.env.PUBLIC_URL + '/img/logo.png'} />.
                  // This should only be used as an escape hatch. Normally you would put
                  // images into the `src` and `import` them in code to get their paths.
                  PUBLIC_URL: publicUrl,
                  // VIE UI 使用的环境变量
                  ...envs
              }
          );
      // Stringify all values so we can feed into Webpack DefinePlugin
      const stringified = {
          "process.env": Object.keys(raw).reduce((env, key) => {
              env[key] = JSON.stringify(raw[key]);
              return env;
          }, {})
      };
  
      return {raw, stringified};
  }
  
  module.exports = getClientEnvironment;
  