gulpfile.js

const gulp = require('gulp'),
    jeditor = require('gulp-json-editor');


function setLocal(cb) {
    setVersion('local');
    cb();
}


function setStaging(cb) {
    setVersion('staging');
    cb();
}


function setProduction(cb) {
    setVersion('production');
    cb();
}


function setVersion(version_name) {
    var jsonData = {
        host: <YOUR_DEFAULT_HOST_NAME> // eg. 'google.com',
        db_host: <YOUR_DEFAULT_DB_HOST> // eg. 'localhost',
        port: <YOUR_DEFAULT_PORT> // eg. '27017',
        db_name: <YOUR_DEFAULT_DB_NAME> // eg. 'student_db',
        db_user: <YOUR_DEFAULT_DB_USER> // eg. 'admin',
        db_password: <YOUR_DEFAULT_DB_PASSWORD> //eg. '1234',
    };
    switch(version_name) {
        case 'production':
            console.log('VERSION =', version_name);
            jsonData.host = <PRODUCTION_HOST>;
            jsonData.db_host = <PRODUCTION_DB_HOST>;
            jsonData.port = <PRODUCTION_PORT>;
            jsonData.db_name = <PRODUCTION_DB_NAME>;
            jsonData.db_user = <PRODUCTION_DB_USER>;
            jsonData.db_password = <PRODUCTION_DB_PASSWORD>;
            break;
        case 'local':
            console.log('VERSION =', version_name);
            jsonData.host = <LOCAL_HOST>;
            jsonData.db_host = <LOCAL_DB_HOST>;
            jsonData.port = <LOCAL_PORT>;
            jsonData.db_name = <LOCAL_DB_NAME>;
            jsonData.db_user = <LOCAL_DB_USER>;
            jsonData.db_password = <LOCAL_DB_PASSWORD>;
            break;
        case 'staging':
            console.log('VERSION =', version_name);
            jsonData.host = <STAGING_HOST>;
            jsonData.db_host = <STAGING_DB_HOST>;
            jsonData.port = <STAGING_PORT>;
            jsonData.db_name = <STAGING_DB_NAME>;
            jsonData.db_user = <STAGING_DB_USER>;
            jsonData.db_password = <STAGING_DB_PASSWORD>;
            break;
        default:
            console.log('DEFAULT VERSION =', version_name);
            jsonData.host = <DEFAULT_HOST>;
            jsonData.db_host = <DEFAULT_DB_HOST>;
            jsonData.port = <DEFAULT_PORT>;
            jsonData.db_name = <DEFAULT_DB_NAME>;
            jsonData.db_user = <DEFAULT_DB_USER>;
            jsonData.db_password = <DEFAULT_DB_PASSWORD>;
            break;
    }
    gulp.src('./config/server.json') // path of your config file which will contain all credentials that we will use in actual code
        .pipe(jeditor(function(json) {
            json.host = jsonData.host;
            json.db_host = jsonData.db_host;
            json.port = jsonData.port;
            json.db_name = jsonData.db_name;
            json.db_user = jsonData.db_user;
            json.db_password = jsonData.db_password;
            return json;
        }))
        .pipe(gulp.dest('./config')); //  Your config folder path
}

exports.local = setLocal;
exports.staging = setStaging;
exports.production = setProduction;