Validate form input text while user write

Question

I would like to validate my form during the writing by user. Now I'm using this javascript:

$(document).ready(function (){
    validate();
    $('#initialKm, #carChassis').change(validate);
});

function validate(){
    if ($('#initialKm').val().length   >   0   &&
            $('#carChassis').val().length  >   0 ){
        $("#saveCarButton").prop("disabled", false);
    }
    else {
        $("#saveCarButton").prop("disabled", true);
    }
}

The only problem is that to execute the validation, after the user has filled the input tag, he has to click elsewhere to activate the button. Is it possible to activate while user fill the field?Thanks

Answer 1

Use $('#initialKm, #carChassis').keyup(validate)

Change only fires after the input focus is lost.

Answer 2

Try using input event

 $(document).ready(function () { validate(); $("#initialKm, #carChassis").on("input", validate); }); function validate() { $("#saveCarButton") .prop("disabled", !$('#initialKm').val().length && !$('#carChassis').val().length); } 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"> </script> <input type="text" id="initialKm" /> <input type="text" id="carChassis" /><br> <button id="saveCarButton">click</button> 

Answer 3

$(document).ready(function () {
    $("#initialKm, #carChassis").keyup(validate);
});

function validate() {
  $("#saveCarButton")
  .prop("disabled", 
   !$('#initialKm').val().length 
    && !$('#carChassis').val().length);
}