Developing Web Apps with Pascal
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….
With the optional ExtP Toolkit, you can turn Lazarus into an ExtPascal IDE.