I use dotenv用于读取环境变量。像这样：

let dotenv = require('dotenv').config({ path: '../../.env' });
console.log(process.env.DB_HOST);

现在我想保存更改.env文件。我找不到任何方法来保存变量.env文件。我应该怎么办？

process.env.DB_HOST = '192.168.1.62';

更新日期：2021 年 8 月

无外部依赖

我一直在寻找类似的解决方案来读取和写入键/值到 .env 文件。我阅读了其他解决方案并编写了两个函数getEnvValue and setEnvValue以简化读/写操作。

To use getEnvValue，.env 文件的格式应如下所示（即周围没有空格= sign):

KEY_1="value 1"
KEY_2="value 2"

const fs = require("fs");
const os = require("os");
const path = require("path");

const envFilePath = path.resolve(__dirname, ".env");

// read .env file & convert to array
const readEnvVars = () => fs.readFileSync(envFilePath, "utf-8").split(os.EOL);

/**
 * Finds the key in .env files and returns the corresponding value
 *
 * @param {string} key Key to find
 * @returns {string|null} Value of the key
 */
const getEnvValue = (key) => {
  // find the line that contains the key (exact match)
  const matchedLine = readEnvVars().find((line) => line.split("=")[0] === key);
  // split the line (delimiter is '=') and return the item at index 2
  return matchedLine !== undefined ? matchedLine.split("=")[1] : null;
};

/**
 * Updates value for existing key or creates a new key=value line
 *
 * This function is a modified version of https://stackoverflow.com/a/65001580/3153583
 *
 * @param {string} key Key to update/insert
 * @param {string} value Value to update/insert
 */
const setEnvValue = (key, value) => {
  const envVars = readEnvVars();
  const targetLine = envVars.find((line) => line.split("=")[0] === key);
  if (targetLine !== undefined) {
    // update existing line
    const targetLineIndex = envVars.indexOf(targetLine);
    // replace the key/value with the new value
    envVars.splice(targetLineIndex, 1, `${key}="${value}"`);
  } else {
    // create new key value
    envVars.push(`${key}="${value}"`);
  }
  // write everything back to the file system
  fs.writeFileSync(envFilePath, envVars.join(os.EOL));
};

// examples
console.log(getEnvValue('KEY_1'));
setEnvValue('KEY_1', 'value 1')