JSFiddle - React, Tailwind, and code Playground

HTML

<div id="testing" contenteditable="true">
  LEADER&nbsp;
</div>

CSS

#testing {
    padding: 5px;
	width: 90%;
	-moz-box-sizing: border-box;
	-webkit-box-sizing: border-box;
	box-sizing: border-box;
	font-size: 13px;
	color: #3B3B3B;
	margin: 0px;
	resize: none;
	overflow: hidden;
	background-color: #FAFAFA;
	line-height: 15px;
	min-height: 42px;
	max-height: 160px;
	outline: none;
}

JavaScript

$('#testing').on('keyup', function(e){
	if($(this).html().indexOf('LEADER ') == 3){
   		
    }else{
    	var splits = $(this).html().split('LEADER ');
        
        $(this).html('LEADER ');
        
        for(var i = 0; i < splits.length; i++){
        	$(this).append(splits[i]);
        }
    }
});