Calculator - js feedback

Any suggestions on refactoring my js? or general feedback?

link: https://codepen.io/bdfoz/pen/XVLJQL

Currently chalking this one up to something weird with JS behavior.

In the console:

.1+.2
//returns 0.30000000000000004
.4+.5
//returns 0.9
.7+.1
// returns 0.7999999999999999

What is that all about?

Resolved this with math.js, referenced in one of the links. Too bad computers don’t speak base-10, or too bad they don’t have infinite memory.

Thanks for going through it with a fine-tooth comb and providing a nice guide to the answer, @camperextraordinaire Really appreciate the thorough feedback/help.