JSFiddle - React, Tailwind, and code Playground

HTML

<div id="ab" style="height:100px;">ab
<div id="cd" style="height:50px;">cd</div>
</div>

JavaScript

var ui = {}; ui.value = 4; 
var k = 4 - 6;

var pixelTop = ui.value;
var pixelTop = ((pixelTop) * (-1));

var ab = $('#ab').height(),
    cd = $('#cd').height(),
    m;
m = cd - ab;
m = m - $('#cd').height();
alert(m);