html5 input event,HTML text input event

In answer to your questions...

The keydown or keypress events can

be intercepted before text is input

using javascript

You can return false after binding a

function to the keydown or keypress

event. This will prevent the text

from being input.

Example using jQuery:

$("#inputfield").live("keydown", function(){

return false;

});

If you want to test some input for value on form submit you can do that using jQuery submit().

$("#theform").submit(function() {

var formval = $("#theinput").val();

if(formval == "") { //or some better test

alert("input value"); //or some other alert...

return false;

} else {

return true;

}

});

Returning false will invalidate the click to submit the form.

Edit:

If as you say in your comments you want to disable the submission of the form until requirements are met for the input field(s)

$("#inputfield").live("keyup", function(){

if($("#inputfield").val() == "") {

$('#button').attr("disabled", true);

} else {

$('#button').attr("disabled", false);

}

});

You want to use the "keyup" event handler to allow the text to be sent first. see my example: on jsbin