Input text form field validation

Hi)
I’m trying to customize my form.
There are 2 input text fields and milti-step form, so i want to validate certain input fields (if visitor taped some number or not), before move forward and before visitor clicks form button “Submit”

If there is a number - button “next step” will be displayed:
Screenshot_2

If input field is empty - button visibility will be “none”:
Screenshot_1

I found some custom code and paste my ID names:

$(‘input’).keyup(function(){
if(($(‘#node45’).val().length > 0) && ($(‘#node46’).val().length > 0))
$(“#simple-button”).css(“display”, “none”);
else
$(“#simple-button”).css(“display”, “block”);
});

but it doesn’t work…
Please, need help)))