JavaScript only client-side Web Part (SPFX)

config.json

{
  "entries": [
    {
      "entry": "./lib/webparts/manual/manual.js",
      "manifest": "./src/webparts/manual/manual.manifest.json",
      "outputPath": "./dist/manual.bundle.js"
    }
  ],
  "externals": {
    "@microsoft/sp-client-base": "node_modules/@microsoft/sp-client-base/dist/sp-client-base.js",
    "@microsoft/sp-client-preview": "node_modules/@microsoft/sp-client-preview/dist/sp-client-preview.js",
    "@microsoft/sp-lodash-subset": "node_modules/@microsoft/sp-lodash-subset/dist/sp-lodash-subset.js",
    "office-ui-fabric-react": "node_modules/office-ui-fabric-react/dist/office-ui-fabric-react.js",
    "react": "node_modules/react/dist/react.min.js",
    "react-dom": "node_modules/react-dom/dist/react-dom.min.js",
    "react-dom/server": "node_modules/react-dom/dist/react-dom-server.min.js"
  },
  "localizedResources": {
  }
}

manual.js

'use strict';
var x = require('@microsoft/sp-client-preview')

var __extends = (this && this.__extends) || function (d, b) {
  for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
  function __() { this.constructor = d; }
  d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};

var manual = function (_super) {
  __extends(manual, _super)
  function manual(context) {
    _super.call(this, context);
  }
  manual.prototype.render = function () {
    this.domElement.innerHTML = 'Hello JavaScript web part';
  }
  return manual;
} (x.BaseClientSideWebPart);
exports.default = manual;

manual.manifes.json

{
  "$schema": "../../../node_modules/@microsoft/sp-module-interfaces/lib/manifestSchemas/jsonSchemas/clientSideComponentManifestSchema.json",

  "id": "3622d9dd-a757-401f-8e61-cee83cc53bec",
  "componentType": "WebPart",
  "version": "0.0.1",
  "manifestVersion": 2,

  "preconfiguredEntries": [{
    "groupId": "3622d9dd-a757-401f-8e61-cee83cc53beb",
    "group": { "default": "Under Development" },
    "title": { "default": "Manual" },
    "description": { "default": "Manual" },
    "officeFabricIconFontName": "Page",
    "properties": {
    }
  }]
}