JSFiddle - React, Tailwind, and code Playground

HTML

Enter domain name: <input type="text" id="domain">

JavaScript

$(document).ready(function(){
  $("input").keyup(function(e){
      var code;
        if (!e) var e = window.event; 
          
        if (e.keyCode) code = e.keyCode; // some browsers use e.keyCode
        else if (e.which) code = e.which;  // others use e.which
    
        if (code == 8 || code == 46)
            return false;
      this.value = this.value.replace('.com', '');
    
      $("#domain").val(this.value + ".com");
      
      var curpos = this.createTextRange();
      curpos.collapse(true);
      curpos.moveEnd('character', this.value.length - 4);
      curpos.select();
  });
});