How to check if all checkboxes are unchecked

The following should do the trick:

var textinputs = document.querySelectorAll('input[type=checkbox]'); 
var empty = [].filter.call( textinputs, function( el ) {
   return !el.checked
});

if (textinputs.length == empty.length) {
    alert("None filled");
    return false;
}