React

https://codepen.io/tbremer/pen/wKpaWe?editors=0010#0

https://codepen.io/marekdano/pen/bVNYpq

Vanilla JS

Live import at https://beta.observablehq.com/@jonasalmeida/i2w

The module source is at https://github.com/mathbiol/i2w/blob/master/calc.js

note how all it takes is to do

Sites update - scripting enabled !!!

Note how Google Site now allows for embedding scripting: