JSFiddle - React, Tailwind, and code Playground

HTML

<pre id="out"></pre>

JavaScript

function circularSum(number, amount, range) {
  var _range = range[1] - range[0] + 1;
  var result = number + amount;
  
  while (result < range[0]) result += _range;
  while (result > range[1]) result -= _range;

	return result;
}

// usage:
var out = document.getElementById('out');

out.innerHTML += '105 - 7   = ' + circularSum(105, -7, [100,110]) + '<br>'; 
out.innerHTML += '105 - 18  = ' + circularSum(105, -18, [100,110]) + '<br>'; 
out.innerHTML += '105 - 118 = ' + circularSum(105, -118, [100,110]) + '<br>'; 

out.innerHTML += '105 + 7   = ' + circularSum(105, +7, [100,110]) + '<br>'; 
out.innerHTML += '105 + 18  = ' + circularSum(105, +18, [100,110]) + '<br>'; 
out.innerHTML += '105 + 118 = ' + circularSum(105, +118, [100,110]) + '<br>';