How to implement “select all” check box in HTML?

Question

I have an HTML page with multiple checkboxes.

I need one more checkbox by the name \"select all\". When I select this checkbox all checkboxes in the HTML page must b

Answer 1

Using jQuery and knockout:

With this binding main checkbox stays in sync with underliying checkboxes, it will be unchecked unless all checkboxes checked.

ko.bindingHandlers.allChecked = {
  init: function (element, valueAccessor) {
    var selector = valueAccessor();

    function getChecked () {
      element.checked = $(selector).toArray().every(function (checkbox) {
        return checkbox.checked;
      });
    }

    function setChecked (value) {
      $(selector).toArray().forEach(function (checkbox) {
        if (checkbox.checked !== value) {
          checkbox.click();
        }
      });
    }

    ko.utils.registerEventHandler(element, 'click', function (event) {
      setChecked(event.target.checked);
    });

    $(window.document).on('change', selector, getChecked);

    ko.utils.domNodeDisposal.addDisposeCallback(element, () => {
      $(window.document).off('change', selector, getChecked);
    });

    getChecked();
  }
};

in html: