JSFiddle - React, Tailwind, and code Playground

by lollero

HTML

<span id="priceToSwap3">$<span>238</span></span>

<select id="trapsize">
 <option data-price="238">foo</option>
 <option data-price="288">foo</option>
</select>

<select id="trapfabric">
 <option data-price="0">foo</option>
 <option data-price="20">foo</option>
</select>

JavaScript

$('#trapfabric, #trapsize').on('change', function() {   
 
    var pricetoSwap = $('#priceToSwap3 span'),
        pricetoSwapTEXT =  pricetoSwap.text(), // Original price
        selected = $(':selected', this);

    pricetoSwap.text( parseInt( pricetoSwapTEXT ) + $(':selected', this).data("price") );
    
});