What knowledge is needed to create a calculator?

Question

css

I know a little HTML5 and CSS3, JavaScript can take a piece there, paste it here to make it work, but I don’t understand the syntax itself yet.
Here I needed a construction calculator to draw up an estimate.
What courses or books do you need to read, go through so that you can create an online calculator on the site. Preferably free.

Answer 1

Start with the simpler things: What is the right way to learn Javascript?

Answer 2

Knowledge of mathematics and algebra to make calculations correctly. You will still write the main code in JS.

Answer 3

programming knowledge required