JSFiddle - React, Tailwind, and code Playground

HTML

<span id="linesCount"></span>
<div contenteditable = "TRUE"></div>

JavaScript

$(".editable").on("keyup", function(keyCode){
    var linesCount = $(".editable div").length + 1;
    $("#linesCount").html(linesCount + " lines.");
    return linesCount;
});