shiny/srcjs/input_binding_radio.js

var radioInputBinding = new InputBinding();
$.extend(radioInputBinding, {
  find: function(scope) {
    return $(scope).find('.shiny-input-radiogroup');
  },
  getValue: function(el) {
    // Select the radio objects that have name equal to the grouping div's id
    return $('input:radio[name="' + $escape(el.id) + '"]:checked').val();
  },
  setValue: function(el, value) {
    $('input:radio[name="' + $escape(el.id) + '"][value="' + $escape(value) + '"]').prop('checked', true);
  },
  getState: function(el) {
    var $objs = $('input:radio[name="' + $escape(el.id) + '"]');

    // Store options in an array of objects, each with with value and label
    var options = new Array($objs.length);
    for (var i = 0; i < options.length; i++) {
      options[i] = { value:   $objs[i].value,
                     label:   this._getLabel($objs[i]) };
    }

    return {
      label:    $(el).parent().find('label[for="' + $escape(el.id) + '"]').text(),
      value:    this.getValue(el),
      options:  options
    };
  },
  receiveMessage: function(el, data) {
    var $el = $(el);

    // This will replace all the options
    if (data.hasOwnProperty('options')) {
      // Clear existing options and add each new one
      $el.find('div.shiny-options-group').remove();
      // Backward compatibility: for HTML generated by shinybootstrap2 package
      $el.find('label.radio').remove();
      $el.append(data.options);
    }

    if (data.hasOwnProperty('value'))
      this.setValue(el, data.value);

    if (data.hasOwnProperty('label'))
      $(el).parent().find('label[for="' + $escape(el.id) + '"]').text(data.label);

    $(el).trigger('change');
  },
  subscribe: function(el, callback) {
    $(el).on('change.radioInputBinding', function(event) {
      callback();
    });
  },
  unsubscribe: function(el) {
    $(el).off('.radioInputBinding');
  },
  // Given an input DOM object, get the associated label. Handles labels
  // that wrap the input as well as labels associated with 'for' attribute.
  _getLabel: function(obj) {
    // If <label><input /><span>label text</span></label>
    if (obj.parentNode.tagName === "LABEL") {
      return $.trim($(obj.parentNode).find('span').text());
    }

    return null;
  },
  // Given an input DOM object, set the associated label. Handles labels
  // that wrap the input as well as labels associated with 'for' attribute.
  _setLabel: function(obj, value) {
    // If <label><input /><span>label text</span></label>
    if (obj.parentNode.tagName === "LABEL") {
      $(obj.parentNode).find('span').text(value);
    }

    return null;
  }

});
inputBindings.register(radioInputBinding, 'shiny.radioInput');