工程配置类

dotenv

Dotenv是一个零依赖模块，它将环境变量从.env文件加载到process.env中。

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安装

# with npm
npm install dotenv

# or with Yarn
yarn add dotenv

在根目录创建一个.env文件，配置格式如下

DB_HOST=localhost
DB_USER=root
DB_PASS=s1mpl3

文件规则

1. BASIC=basic 变为 {BASIC: 'basic'}
2. 空行会被跳过
3. lines beginning with # are treated as comments
4. empty values become empty strings (EMPTY= becomes {EMPTY: ''})
5. inner quotes are maintained (think JSON) (JSON={"foo": "bar"} becomes {JSON:"{"foo": "bar"}")
6. whitespace is removed from both ends of unquoted values (see more on trim) (FOO= some value becomes {FOO: 'some value'})
7. single and double quoted values are escaped (SINGLE_QUOTE='quoted' becomes {SINGLE_QUOTE: "quoted"})
8. single and double quoted values maintain whitespace from both ends (FOO=" some value " becomes {FOO: ' some value '})
9. double quoted values expand new lines (MULTILINE="new\nline" becomes

使用

const dotenv = require('dotenv')
dotenv.config()
console.log(process.env.DB_HOST)

config 参数设置

设定需要转换的配置文件，默认是.env

dotenv.config({
  path: path.resolve(process.cwd(), '.env.production'),
});

其它方法

parse 从其它来源获取的配置，通过Parse转换得到json, 例如通过fs.readFile读取，或者通过buffer

const dotenv = require('dotenv')
const buf = Buffer.from('BASIC=basic')
const config = dotenv.parse(buf) // will return an object
console.log(typeof config, config) // object { BASIC : 'basic' }

如果设置的变量与环境变量重复，环境变量将被保留（不会覆盖)

但有方法可以不这么做。使用文件读取，动态设置到process.env中

const fs = require('fs')
const dotenv = require('dotenv')
const envConfig = dotenv.parse(fs.readFileSync('.env.override'))
for (const k in envConfig) {
  process.env[k] = envConfig[k]
}