JSFiddle - React, Tailwind, and code Playground

HTML

<div class="within">
  <div class="red"></div>
  <div class="blue"></div>    
</div>

CSS

.red {
    background: red;
    width: 200px;
    height: 50px;
}
.blue {
    background: blue;
    height: 100px;
    width: 100px;
    margin-left : 100.6px;
}
.within {
    background: #bbb;
    height: 250px;
    width : 250px;
}

JavaScript

$( window ).on( "load", function() {
/*!
 * jQuery UI Position
 * http://jqueryui.com
 *
 * Copyright 2014 jQuery Foundation and other contributors
 * Released under the MIT license.
 * http://jquery.org/license
 *
 * http://api.jqueryui.com/position/
 */

/*! Patched by NetMatch to fix subpixel alignment reporting */

(function( factory ) {
	if ( typeof define === "function" && define.amd ) {

		// AMD. Register as an anonymous module.
		define( [ "jquery" ], factory );
	} else {

		// Browser globals
		factory( jQuery );
	}
}(function( $ ) {

	$.ui = $.ui || {};

	var cachedScrollbarWidth, supportsOffsetFractions,
		max = Math.max,
		abs = Math.abs,
		round = Math.round,
		rhorizontal = /left|center|right/,
		rvertical = /top|center|bottom/,
		roffset = /[\+\-]\d+(\.[\d]+)?%?/,
		rposition = /^\w+/,
		rpercent = /%$/,
		_position = $.fn.position;

	function getOffsets( offsets, width, height ) {
		return [
			parseFloat( offsets[ 0 ] ) * ( rpercent.test( offsets[ 0 ] ) ? width / 100 : 1 ),
			parseFloat( offsets[ 1 ] ) * ( rpercent.test( offsets[ 1 ] ) ? height / 100 : 1 )
		];
	}

	function parseCss( element, property ) {
		return parseInt( $.css( element, property ), 10 ) || 0;
	}

	function getDimensions( elem ) {
		var raw = elem[0];
		if ( raw.nodeType === 9 ) {
			return {
				width: elem.width(),
				height: elem.height(),
				offset: { top: 0, left: 0 }
			};
		}
		if ( $.isWindow( raw ) ) {
			return {
				width: elem.width(),
				height: elem.height(),
				offset: { top: elem.scrollTop(), left: elem.scrollLeft() }
			};
		}
		if ( raw.preventDefault ) {
			return {
				width: 0,
				height: 0,
				offset: { top: raw.pageY, left: raw.pageX }
			};
		}
		return {
			width: elem.outerWidth(),
			height: elem.outerHeight(),
			offset: elem.offset()
		};
	}

	$.position = {
		scrollbarWidth: function() {
			if ( cachedScrollbarWidth !== undefined ) {
				return cachedScrollbarWidth;
			}
			var w1, w2,
				div = $( "<div...