JSFiddle - React, Tailwind, and code Playground

HTML

<input type="number" id="strScore1" class="attribScore" min=8 max=15>
 <input type="number" id="strMod1" class="attribMod" readonly="readonly">
   <br>
   <br>
 <input type="number" id="strScore2" class="attribScore" min=8 max=15>
 <input type="number" id="strMod2" class="attribMod" readonly="readonly">

JavaScript

$(".attribScore").bind({
    'input':function(){
        var attrib_num = this.id.substring(8,this.length);  
        $('#strMod' + attrib_num).val((Math.floor(this.value / 2) - 5));
    }
});