JSFiddle - React, Tailwind, and code Playground

HTML

<!--INLINE EVENT-->

<input type="text" value="" onKeyDown="if(event.keyCode==13) alert('Inline Event');" size="20" id="demo1" placeholder="Inline Event">
 
<!--UNOBTRUSIVE CODE USING ADDEVENTLISTENER-->
    
<input type="text" id="demo2" value="" size="20" placeholder="Using addEventListener">

<!--UNOBTRUSIVE CODE CALLING FUNCTION-->
    
<input type="text" id="demo3" value="" onKeyUp="executeEvent(this,value)" size="20" placeholder="Seperate Handler">

JavaScript

document.getElementById('demo2').addEventListener('keydown',function(event) {
    if (event.keyCode == 13) {
        alert('5');
    }
})


function executeEvent(elem,value){
 console.log(elem)
if (event.keyCode == 13) {
        alert('You entered ' +elem.value);
    }
}