JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test">test</div>
<div id="result"></div>

JavaScript

var elem = document.getElementById('test'),
    result = document.getElementById('result'),
    oneClick = 0,
    twoClick;
//alert(new Date().getTime());
function handler () {
    if(oneClick === 0){
        oneClick = new Date().getTime()/1000;
       // alert(oneClick);
    }else{
        var intervalClick;
        twoClick = new Date().getTime()/1000;
      //  alert('one click:    ' +oneClick+ '/n two click:   ' +twoClick)
        intervalClick = twoClick - oneClick;
        alert('interval click:   ' +intervalClick);
        oneClick = 0;
    }
}
document.body.onkeydown = handler;