JSFiddle - React, Tailwind, and code Playground

by Gabriele Petrioli

HTML

<form name="testForm" action="" method="post">
            <select name="combo1" id="combo1">
                <option value="Yes">Yes</option>
                <option value="No">No</option>
            </select><br /><br />
            <select name="combo2" id="combo2">
                <option value="Yes">Yes</option>
                <option value="No">No</option>
            </select>
        </form>

JavaScript

window.onload = function() { BindEvent(); }

    function BindEvent()
    {
        var c1 = document.getElementById ( 'combo1' );
        var c2= document.getElementById ( 'combo2' );
        
        c1.onchange = invert;
        c2.onchange = invert;
        
        c1.onchange();
    }
            
    function invert() { 
             var otherElem = document.getElementById( (this.id=='combo1')? 'combo2' : 'combo1');
             otherElem.value = (this.value=='Yes')?'No':'Yes';
             console.log(this);
        }