How to check if all checkboxes are unchecked

Here, a short and very simple example (Vanilla Javascript):

if (document.querySelectorAll('input[type="checkbox"]:checked').length === document.querySelectorAll('input[type="checkbox"]').length) {
    console.log('All checkboxes are checked');
} else {
    console.log('Some checkboxes are not checked');
}

Here in jQuery syntax:

if ($('input[type="checkbox"]:checked').length === $('input[type="checkbox"]').length) {
    console.log('All checkboxes are checked');
} else {
    console.log('Some checkboxes are not checked');
}

Another way to do it, with the :not() pseudo-selector:

if (document.querySelectorAll('input[type="checkbox"]:not(:checked)').length) {
    console.log('Some checkbox are not checked');
}

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;
}

You can simplify a little, given that you're able to use querySelectorAll():

var checked = document.querySelectorAll('input:checked');

if (checked.length === 0) {
    // there are no checked checkboxes
    console.log('no checkboxes checked');
} else {
    // there are some checked checkboxes
    console.log(checked.length + ' checkboxes checked');
}

JS Fiddle (with no checkboxes checked).

JS Fiddle (with some checkboxes checked).

Or, if all you want is a Boolean value to indicate whether any checkbox is checked, for use in a function:

var isChecked = document.querySelectorAll('input:checked').length === 0 ? false : true;
return isChecked;

Proof-of-concept demo.

You could, of course, avoid creating a variable and simply return the result of the ternary; I only used the variable to try and make it clear what, precisely, I was returning/testing-for.

Reference:

• :checked pseudo-class.