Function not found when using WebPack

Question

On an HTML page I have the following:

<button onclick="openAlert()">Open</button>

And a scripts.js file with an openAlert function:

function openAlert() {
  alert("Alert is opened");
}

When I click the button the Alert opens as expected.

I then used Webpack to minify scripts.js file using webpack.config:

const webpack = require('webpack');

var UglifyJsPlugin = require('uglifyjs-webpack-plugin');

module.exports = {

  resolve: {
    extensions: ['.js'],
  },

  entry: {
    'scripts.min': './scripts/scripts.js',
  },  

  output: {
    path:  __dirname + '/dist',
    filename: '[name].js'
  },

  optimization: {
    minimizer: [    
      new UglifyJsPlugin({
        cache: true,
        parallel: true,
        sourceMap: false
      })
    ]
  },

};

The scripts.min.js file is created and correctly loaded on the page.

But when I click the button I get the following error:

ReferenceError: Can't find variable openAlert

What am I doing wrong?

The generated scripts.min.js file is:

/******/ (function(modules) { // webpackBootstrap
/******/    // The module cache
/******/    var installedModules = {};
/******/
/******/    // The require function
/******/    function __webpack_require__(moduleId) {
/******/
/******/        // Check if module is in cache
/******/        if(installedModules[moduleId]) {
/******/            return installedModules[moduleId].exports;
/******/        }
/******/        // Create a new module (and put it into the cache)
/******/        var module = installedModules[moduleId] = {
/******/            i: moduleId,
/******/            l: false,
/******/            exports: {}
/******/        };
/******/
/******/        // Execute the module function
/******/        modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);
/******/
/******/        // Flag the module as loaded
/******/        module.l = true;
/******/
/******/        // Return the exports of the module
/******/        return module.exports;
/******/    }
/******/
/******/
/******/    // expose the modules object (__webpack_modules__)
/******/    __webpack_require__.m = modules;
/******/
/******/    // expose the module cache
/******/    __webpack_require__.c = installedModules;
/******/
/******/    // define getter function for harmony exports
/******/    __webpack_require__.d = function(exports, name, getter) {
/******/        if(!__webpack_require__.o(exports, name)) {
/******/            Object.defineProperty(exports, name, { enumerable: true, get: getter });
/******/        }
/******/    };
/******/
/******/    // define __esModule on exports
/******/    __webpack_require__.r = function(exports) {
/******/        if(typeof Symbol !== 'undefined' && Symbol.toStringTag) {
/******/            Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' });
/******/        }
/******/        Object.defineProperty(exports, '__esModule', { value: true });
/******/    };
/******/
/******/    // create a fake namespace object
/******/    // mode & 1: value is a module id, require it
/******/    // mode & 2: merge all properties of value into the ns
/******/    // mode & 4: return value when already ns object
/******/    // mode & 8|1: behave like require
/******/    __webpack_require__.t = function(value, mode) {
/******/        if(mode & 1) value = __webpack_require__(value);
/******/        if(mode & 8) return value;
/******/        if((mode & 4) && typeof value === 'object' && value && value.__esModule) return value;
/******/        var ns = Object.create(null);
/******/        __webpack_require__.r(ns);
/******/        Object.defineProperty(ns, 'default', { enumerable: true, value: value });
/******/        if(mode & 2 && typeof value != 'string') for(var key in value) __webpack_require__.d(ns, key, function(key) { return value[key]; }.bind(null, key));
/******/        return ns;
/******/    };
/******/
/******/    // getDefaultExport function for compatibility with non-harmony modules
/******/    __webpack_require__.n = function(module) {
/******/        var getter = module && module.__esModule ?
/******/            function getDefault() { return module['default']; } :
/******/            function getModuleExports() { return module; };
/******/        __webpack_require__.d(getter, 'a', getter);
/******/        return getter;
/******/    };
/******/
/******/    // Object.prototype.hasOwnProperty.call
/******/    __webpack_require__.o = function(object, property) { return Object.prototype.hasOwnProperty.call(object, property); };
/******/
/******/    // __webpack_public_path__
/******/    __webpack_require__.p = "";
/******/
/******/
/******/    // Load entry module and return exports
/******/    return __webpack_require__(__webpack_require__.s = "./wwwroot/scripts/scripts.js");
/******/ })
/************************************************************************/
/******/ ({

/***/ "./wwwroot/scripts/scripts.js":
/*!************************************!*\
  !*** ./wwwroot/scripts/scripts.js ***!
  \************************************/
/*! no static exports found */
/***/ (function(module, exports) {

eval("function openAlert() {\n  alert(\"Alert is opened\");\n}\n\n//# sourceURL=webpack:///./wwwroot/scripts/scripts.js?");

/***/ })

/******/ }); 

Answer 1

It's because webpack create all variables in own scope.

you can see

(function(modules) { 

 ...code

}); // end of scope 

you can get out from scope if you add your function in window scope

example window.openAlert = function(){...}

But it's bad practice

Or you need import in html file this function and then you need add HTML loader in webpack