Skip to main content

如何访问和转换环境变量

🌐 How to access and cast environment variables

在大多数用例中，环境之间会有不同的配置（例如数据库凭据）。

🌐 In most use cases there will be different configurations between environments (e.g. database credentials).

与其将这些凭据写入配置文件，不如在应用根目录的 .env 文件中定义变量：

🌐 Instead of writing those credentials into configuration files, variables can be defined in a .env file at the root of the application:

# path: .env

DATABASE_PASSWORD=acme

要自定义要加载的 .env 文件路径，请在启动应用之前设置一个名为 ENV_PATH 的环境变量：

🌐 To customize the path of the .env file to load, set an environment variable called ENV_PATH before starting the application:

ENV_PATH=/absolute/path/to/.env npm run start

访问环境变量​

🌐 Accessing environment variables

在 .env 文件中定义的变量可以在配置文件和应用文件中的任何地方使用 process.env.{variableName} 访问。

🌐 Variables defined in the .env file are accessible using process.env.{variableName} anywhere in configuration and application files.

在配置文件中，env() 工具允许定义默认值和转换值：

🌐 In configuration files, a env() utility allows defining defaults and casting values:

./config/database.js

module.exports = ({ env }) => ({
  connections: {
    default: {
      settings: {
        password: env('DATABASE_PASSWORD'),
      },
    },
  },
});
Note

语法 property-name: env('VAR', 'default-value') 使用存储在 .env 文件中的值。如果在 .env 文件中没有指定值，则使用默认值。

🌐 The syntax property-name: env('VAR', 'default-value') uses the value stored in the .env file. If there is no specified value in the .env file the default value is used.

设置环境变量​

🌐 Casting environment variables

env() 工具可用于将环境变量转换为不同类型：

🌐 The env() utility can be used to cast environment variables to different types:

// Returns the env if defined without casting it
env('VAR', 'default');

// Cast to integer (using parseInt)
env.int('VAR', 0);

// Cast to float (using parseFloat)
env.float('VAR', 3.14);

// Cast to boolean (check if the value is equal to 'true')
env.bool('VAR', true);

// Cast to JS object (using JSON.parse)
env.json('VAR', { key: 'value' });

// Cast to array (syntax: ENV_VAR=[value1, value2, value3] | ENV_VAR=["value1", "value2", "value3"])
env.array('VAR', [1, 2, 3]);

// Cast to date (using new Date(value))
env.date('VAR', new Date());

// Returns the env matching oneOf union types
env.oneOf('UPLOAD_PROVIDER', ['local', 'aws'], 'local')