The ultimate goal is to use Lazarus to create a webpage in a RAD manner as much as possible. There can be several approaches to this.
- Create an actual LCL widgetset
- Do not use the actual LCL widgetset, but create a widgetset that uses the IDE support for a custom designer.
- Do not use the actual LCL widgetset, but create one that supports Pas2JS app development in the browser.
Either way, a set of basic widgets that can be used in HTML are needed.
Currently, several efforts are underway to create such a widget set.
in random order, they are:
- ProjJ:  Warley Alex
- XComponents (and XIDE):  (Stephen Wright)
- Pas2JS Widgetset: A project based on LLCL  (Heliosroots)
- Based on DHTMLX:  (Christian Ulrich)
Most freeware tools for Lazarus Web Application lack of features and documentations. If you really need a good component for Web Application then TMS Web Core is worth to try.
- TMS software has created: TMS Web Core
- Install TMS Web Core to Lazarus:https://www.youtube.com/watch?v=YzZazLnF8Zk
- TMS Web Core Developer Guide: http://www.tmssoftware.biz/Download/Manuals/TMSWEBCoreDevGuide.pdf
XIDE is a simple, stand alone, open source IDE for Free Pascal which runs in the browser (and on other platforms supported by Lazarus).
It is a combined Client Side Run Time Library and RAD IDE intended to allow Pascal(Pas2JS) and/or Python(Pyodide) development with the minimum of installation or learning curve while also being as platform independent as possible. XComponents is the widgetset that enables XIDE.
XIDE is intended for Prototyping, Small Group Collaboration and Agile Line of Business projects where the choice of browser can be specified. It will run on any platform that is supported by Chrome or Electron, or Lazarus(+CEF). It is not intended for the development of general-purpose public facing web sites. It may also run on other HTML5 browsers (e.g. Microsoft Edge), but this is not tested.
XIDESimplePascalExample.html  XIDESimplePythonExample.html  XIDEPascalSVGAndGPUExample.html 
To build from source….
Pas2JS Widgetset is a RAD Framework to develop Web Applications like to develop Windows Applications.
1. Download from: https://github.com/heliosroots/Pas2JS_Widget
2. Extract to Lazarus - pas2js_designer
3. Open: Lazarus - pas2js_designer - package: pas2js_designer_package.lpk
4. Click on Use - Install
5. Click on Yes to install this package
6. You will see LCL for pas2js!