Validate html text input as it's typed

Question

What\'s the best way of validating an HTML text input as it\'s typed? All ways I know of doing it has some drawbacks:

1. Using $.keypress you only

Answer 1

let that=this;

$(this.element).find("input").keypress(function(e) {
               let character = String.fromCharCode(e.keyCode);

               let newValue =  this.value.substring(0,this.selectionStart) + character + this.value.substring(this.selectionEnd, String(this.value).length);


               if (!that.isFormatValid(newValue, that.getdecimalPoints())) {
                     e.preventDefault();
                     e.stopPropagation();
                     return false;
              }

              return true;
        });


        $(this.element).find("input").bind({
              paste: function() {
                     let _this = this;

                     setTimeout( function() {
                           let decimals = that.getdecimalPoints();
                           if (!that.isFormatValid($(_this).val(), decimals)) {                        
                                         $(_this).val('');                        
                           }
                     }, 0);                                                                                                  
                  }
           });