desactivar boton enviar

en caso de no estar selecionados todos los checkbox, desactiva el boton enviar

by Felipe Zura

HTML

<input type="checkbox" name="test" /> 
<br />
<input type="checkbox" name="test2" /> 

<br />
<input type="checkbox" name="test3" /> 

<br /><br />
<input type="button" id="button" value="send" />

JavaScript

$(function () {
    var button = $('#button').prop('disabled', true);
    var radios = $('input[type="checkbox"]');
    var arr    = $.map(radios, function(el) { 
                return el.name; 
              });

    var groups = $.grep(arr, function(v, k){
            return $.inArray(v ,arr) === k;
    }).length;

    radios.on('change', function () {
        button.prop('disabled', radios.filter(':checked').length < groups);
    });
});