title: import momentjs with es6 modules and webpack Cannot assign to read only property
body: <p>I did following steps</p>
  
  <pre><code>npm install moment --save
  import moment from "moment"
  </code></pre>
  
  <p>When i want to import momentjs i get the following error:</p>
  
  <pre><code>Uncaught TypeError: Cannot assign to read only property 'clone' of object '#&lt;Moment&gt;' (moment.js:3837 )
  </code></pre>
  
  <p>moment version: ^2.22.1</p>
  
  <p>I use webpack 4.</p>
  
  <p>Trying to import like this also failed with the same error:</p>
  
  <pre><code>import moment from "moment/src/moment"
  </code></pre>
  
  <p>Can somebody help me? I really dont know how to solve this.
  My Webpack Config:</p>
  
  <pre><code>const path = require('path')
  const BrowserSyncPlugin = require("browser-sync-webpack-plugin")
  var webpack = require('webpack');
  const BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin;
  
  module.exports = {
    entry: './src/js/index.js',
    output: {
      path: path.resolve(__dirname, 'static'),
      filename: 'monitor-bundle.js'
  
    },
    devtool: 'source-map',
    mode: 'development',
  
    module: {
      rules: [
        {
          test: /\.js$/,
          exclude: /node_modules/,
          use: {
            loader: "babel-loader"
          }
        },
  
        {
          test: /\.css$/,
        }
      ]
    },
    watch: true,
    plugins: [
      new BrowserSyncPlugin({
        watchOptions: {
          poll: true
        },
          host: "localhost",
          port: "1337",
          proxy: "http://localhost:80/",
          files: ["./static/monitor-bundle.js"],
          open: true,
          reloadDelay: 0,
          reloadDebounce: 0,
          browser: ["chromium", "google chrome"]
      }),
      new BundleAnalyzerPlugin(),
  ],
  };
  </code></pre>