window.ENTITIES={'/api/snippets/javascript/node.js%20-%20custom%20simple%20solution%20to%20read%20.env%20file':[{"result":true,"message":null,"batch":{"type":"javascript","name":"node.js - custom simple solution to read .env file","items":[{"id":"1Ae4Z1","type":"javascript","name":"Node.js - custom simple solution to read .env file","content":"// ---------------------------------------------------------\n// index.js file:\n// ---------------------------------------------------------\n\nconst {initializeVariables, ENV_PATH} = require('./env');\n\nconst ENV_CONSTANTS = exports.ENV_CONSTANTS = {\n    __dirname: () => __dirname,           // use it in `.env` file as %__dirname%\n    __filename: () => __filename          // use it in `.env` file as %__filename%\n};\n\ninitializeVariables(ENV_PATH, ENV_CONSTANTS);  // ENV_CONSTANTS enables constant values injection (we can use e.g. VARIABLE_NAME=%CONSTANT_NAME%)\n\nconsole.log(process.env.BACKEND_PATH);\nconsole.log(process.env.FRONTEND_PATH);\n\n\n// Example output:\n//\n//     /opt/my-website/backend\n//     /opt/my-website/frontend\n\n\n\n// ---------------------------------------------------------\n// .env file:\n// ---------------------------------------------------------\n\nAPPLICATION_PATH=%__dirname%\n\nBACKEND_PATH=$APPLICATION_PATH$/backend\nFRONTEND_PATH=$APPLICATION_PATH$/frontend\n\n\n\n// ---------------------------------------------------------\n// env.js file:\n// ---------------------------------------------------------\n\nconst fs = require('fs');\n\n\nconst NEWLINE_EXPRESSION = /\\r?\\n/g;\n\n// Syntax:\n//\n//   %NODE_CONSTANT_NAME%    - constant defined in application source code\n//   $LOCAL_VARIABLE_NAME$   - variable defined in `.env` file\n//   *GLOBAL_VARIABLE_NAME*  - variable defined in `process.env` object\n//\nconst REFERENCE_EXPRESSION = /%%|%([^%*$]+)%|%|\\*\\*|\\*([^%*$]+)\\*|\\*|\\$\\$|\\$([^%*$]+)\\$|\\$/g;\n\nconst ENV_PATH = exports.ENV_PATH = '.env';\n\n\nconst iterateVariables = exports.iterateVariables = (text, callback) => {\n    const lines = text.split(NEWLINE_EXPRESSION);\n    for (let i = 0; i < lines.length; ++i) {\n        const line = lines[i];\n        if (line) {\n            const index = line.indexOf('=');\n            if (index !== -1) {\n                const name = line.substring(0, index);\n                if (name) {\n                    const value = line.substring(index + 1);\n                    callback(name, value, i);\n                }\n            }\n        }\n    }\n};\n\nconst readVariables = exports.readVariables = (path = ENV_PATH, constants = {}) => {\n    const text = fs.readFileSync(path, 'utf-8');\n    const variables = [];\n    const environment = process.env;\n    iterateVariables(text, (name, value, index) => {\n        const action = (match, group1, group2, group3) => {\n            switch (match) {\n                case '%': throw new Error(`Incorrect '%' character usage in 'name=${value}' line (line number: ${index + 1}).`);\n                case '*': throw new Error(`Incorrect '*' character usage in 'name=${value}' line (line number: ${index + 1}).`);\n                case '$': throw new Error(`Incorrect '$' character usage in 'name=${value}' line (line number: ${index + 1}).`);\n                case '%%': return '%';\n                case '**': return '*';\n                case '$$': return '$';\n                default:\n                    switch (match[0]) {\n                        case '%':\n                            {\n                                const constant = constants[group1];\n                                if (constant) {\n                                    return constant();\n                                }\n                                throw new Error(`Unknown '%${group1}%' environment constant.`);\n                            }\n                        case '*':\n                            {\n                                const variable = environment[group2];\n                                if (variable == null) {  // null or undefined\n                                    throw new Error(`Unknown '%${group2}%' environment variable.`);\n                                }\n                                return variable;\n                            }\n                        case '$':\n                            {\n                                const variable = variables[group3];\n                                if (variable == null) {  // null or undefined\n                                    throw new Error(`Unknown '$${group3}$' environment variable.`);\n                                }\n                                return variable;\n                            }\n                        default:\n                            throw new Error(`Unknown constant/variable type.`);\n                    }\n            }\n        };\n        variables[name] = value.replace(REFERENCE_EXPRESSION, action);\n    });\n    return variables;\n};\n\nconst initializeVariables = exports.initializeVariables = (path = ENV_PATH, constants = null) => {\n    const variables = readVariables(path, constants);\n    const keys = Object.keys(variables);\n    for (const key of keys) {\n        process.env[key] = variables[key];\n    }\n};","source":"https://dirask.com/posts/Node-js-read-env-file-custom-solution-D7oyOD","author":{"id":"ZDxWG0","name":"Hayley-Mooney","avatar":"1629030405629__ZDxWG0__w40px_h40px.png","points":677,"role":"BASIC"},"creationTime":1676151471000,"updateTime":1676260526000,"removalTime":null}]}}]};