JSFiddle - React, Tailwind, and code Playground

HTML

<textarea class="typing-only" data-temp=""></textarea>

JavaScript

$(document).on('input', '.typing-only', function(){
    if((this.value.length - 1) > $(this).data('temp').length){
        alert('Cheat!');
    }
    $(this).data('temp', this.value);
});