JSFiddle - React, Tailwind, and code Playground

HTML

<div style="width:200px;height:150px;background-color:#eeeeee;" id="outer">
  <div style="width:400px;">
    <button style="width:130px;">Button AAAAAAA</button>
    <button style="width:130px;">Button BBBBBBB</button>
    <button style="width:130px;">Button CCCCCCC</button>
  </div>
</div>

CSS

/*
== malihu jquery custom scrollbar plugin ==
Plugin URI: http://manos.malihu.gr/jquery-custom-content-scroller
*/



/*
CONTENTS: 
	1. BASIC STYLE - Plugin's basic/essential CSS properties (normally, should not be edited). 
	2. VERTICAL SCROLLBAR - Positioning and dimensions of vertical scrollbar. 
	3. HORIZONTAL SCROLLBAR - Positioning and dimensions of horizontal scrollbar.
	4. VERTICAL AND HORIZONTAL SCROLLBARS - Positioning and dimensions of 2-axis scrollbars. 
	5. TRANSITIONS - CSS3 transitions for hover events, auto-expanded and auto-hidden scrollbars. 
	6. SCROLLBAR COLORS, OPACITY AND BACKGROUNDS 
		6.1 THEMES - Scrollbar colors, opacity, dimensions, backgrounds etc. via ready-to-use themes.
*/



/* 
------------------------------------------------------------------------------------------------------------------------
1. BASIC STYLE  
------------------------------------------------------------------------------------------------------------------------
*/

	.mCustomScrollbar{ -ms-touch-action: pinch-zoom; touch-action: pinch-zoom; /* direct pointer events to js */ }
	.mCustomScrollbar.mCS_no_scrollbar, .mCustomScrollbar.mCS_touch_action{ -ms-touch-action: auto; touch-action: auto; }
	
	.mCustomScrollBox{ /* contains plugin's markup */
		position: relative;
		overflow: hidden;
		height: 100%;
		max-width: 100%;
		outline: none;
		direction: ltr;
	}

	.mCSB_container{ /* contains the original content */
		overflow: hidden;
		width: auto;
		height: auto;
	}



/* 
------------------------------------------------------------------------------------------------------------------------
2. VERTICAL SCROLLBAR 
y-axis
------------------------------------------------------------------------------------------------------------------------
*/

	.mCSB_inside > .mCSB_container{ margin-right: 30px; }

	.mCSB_container.mCS_no_scrollbar_y.mCS_y_hidden{ margin-right: 0; } /* non-visible scrollbar */
	
	.mCS-dir-rtl > .mCSB_inside > .mCSB_container{ /* RTL...

JavaScript

/* == jquery mousewheel plugin == Version: 3.1.13, License: MIT License (MIT) */
!function(a){"function"==typeof define&&define.amd?define(["jquery"],a):"object"==typeof exports?module.exports=a:a(jQuery)}(function(a){function b(b){var g=b||window.event,h=i.call(arguments,1),j=0,l=0,m=0,n=0,o=0,p=0;if(b=a.event.fix(g),b.type="mousewheel","detail"in g&&(m=-1*g.detail),"wheelDelta"in g&&(m=g.wheelDelta),"wheelDeltaY"in g&&(m=g.wheelDeltaY),"wheelDeltaX"in g&&(l=-1*g.wheelDeltaX),"axis"in g&&g.axis===g.HORIZONTAL_AXIS&&(l=-1*m,m=0),j=0===m?l:m,"deltaY"in g&&(m=-1*g.deltaY,j=m),"deltaX"in g&&(l=g.deltaX,0===m&&(j=-1*l)),0!==m||0!==l){if(1===g.deltaMode){var q=a.data(this,"mousewheel-line-height");j*=q,m*=q,l*=q}else if(2===g.deltaMode){var r=a.data(this,"mousewheel-page-height");j*=r,m*=r,l*=r}if(n=Math.max(Math.abs(m),Math.abs(l)),(!f||f>n)&&(f=n,d(g,n)&&(f/=40)),d(g,n)&&(j/=40,l/=40,m/=40),j=Math[j>=1?"floor":"ceil"](j/f),l=Math[l>=1?"floor":"ceil"](l/f),m=Math[m>=1?"floor":"ceil"](m/f),k.settings.normalizeOffset&&this.getBoundingClientRect){var s=this.getBoundingClientRect();o=b.clientX-s.left,p=b.clientY-s.top}return b.deltaX=l,b.deltaY=m,b.deltaFactor=f,b.offsetX=o,b.offsetY=p,b.deltaMode=0,h.unshift(b,j,l,m),e&&clearTimeout(e),e=setTimeout(c,200),(a.event.dispatch||a.event.handle).apply(this,h)}}function c(){f=null}function d(a,b){return k.settings.adjustOldDeltas&&"mousewheel"===a.type&&b%120===0}var e,f,g=["wheel","mousewheel","DOMMouseScroll","MozMousePixelScroll"],h="onwheel"in document||document.documentMode>=9?["wheel"]:["mousewheel","DomMouseScroll","MozMousePixelScroll"],i=Array.prototype.slice;if(a.event.fixHooks)for(var j=g.length;j;)a.event.fixHooks[g[--j]]=a.event.mouseHooks;var k=a.event.special.mousewheel={version:"3.1.12",setup:function(){if(this.addEventListener)for(var c=h.length;c;)this.addEventListener(h[--c],b,!1);else...