JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://maps.googleapis.com/maps/api/js?v=3&amp;amp;sensor=false"></script>
<div class="flexbox-container">
  <div id="left_container" class="scrollMap"></div>
  <div id="map_canvas"></div>
</div>

CSS

.flexbox-container {
  height: 90vh;
  position: relative;
}

#left_container {
  padding: 0 5px;
  overflow-y: auto;
  display: inline-block;
  height: 100%;
  border-right: 200px transparent solid;
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 1;
  pointer-events: none;
}

#left_container.scrollMap {
  pointer-events: auto;
}

#map_canvas {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  width: 200px;
}

JavaScript

var post = "<h3>Post title</h3><div>Donec id elit non mi porta gravida at eget metus. Maecenas sed diam eget risus varius blandit.</div><hr>";
  var i = 0;
  while (i < 10) { $('#left_container').append(post); i++; }

  var map_canvas = $('#map_canvas')[0],
      $left_container = $('#left_container'),
      $parent = $('.flexbox-container'),
  		options = {
    		zoom: 10,
    		scrollwheel: false,
    		center: new google.maps.LatLng(49, 17)
  		},
      map = new google.maps.Map(map_canvas, options),
      wheelEvent = function (e) {
        $left_container.addClass('scrollMap');
    	};
  
  map_canvas.addEventListener('mousewheel', wheelEvent);
  map_canvas.addEventListener('DOMMouseScroll', wheelEvent);
  $parent.mousemove(function (e) {
    if (e.clientX < $parent.width() - 200) {
      $left_container.addClass('scrollMap');
    } else {
      $left_container.removeClass('scrollMap');
    }    
  });