JSFiddle - React, Tailwind, and code Playground

HTML

<p>
 fjklsdajfksjdafkljksldjaf fkljsdaklfjkldsjf
 </p>
 
 <div id='editor' style='' contenteditable="true">
          <p><b>Lorem</b> <i>ipsum</i> <u>dolor</u> <strike>sit</strike> amet, consectetur adipisicing elit. Necessitatibus natus vero voluptatem aliquam molestias dicta aperiam dignissimos laudantium accusamus saepe!</p>
        </div>
        
        
        <button onClick="Check()"> Get Selected Text </button>
        
        </button>

JavaScript

function Check()
{
alert(window.getSelection().anchorNode.data.substring( window.getSelection().anchorOffset,window.getSelection().extentOffset ))

}