摘要：省略，是核心，以下為部分核心代碼上面為和添加上為監聽器函數這個屬性不用初始化，可以在焦點改變時修改

HTML

  
    
    
    
    
    
  
  

    

      

        Name:
        
      

      
Drink Options

      

        

          Water
        
        

          Tea
        
        

          Coffee
        
        

          Cola
        
        

          Ginger Ale
        
      

      

        Order a drink
      

    

    

  

省略css，js是核心，以下為部分核心js代碼

  function RadioGroup(id) {
    this.el = document.querySelector(id);
    this.buttons = slice(this.el.querySelectorAll(".radio"));
    this.focusedIdx = 0;
    this.focusedButton = this.buttons[this.focusedIdx];

    this.el.addEventListener("keydown", this.handleKeyDown.bind(this));
    this.el.addEventListener("click", this.handleClick.bind(this));

    // Set ARIA role for the radio group.
    this.el.setAttribute("role", "radiogroup");

    var firstButton = true;
    for (var button of this.buttons) {
      if (firstButton) {
        button.tabIndex = "0";
        firstButton = false;
      } else {
        button.tabIndex = "-1";
      }
    // Set ARIA role for the radio.
      button.setAttribute("role", "radio");
    }
  }

上面為radiogroup和radio添加role

RadioGroup.prototype.handleKeyDown = function(e) {
  switch(e.keyCode) {

    case VK_UP:
    case VK_LEFT: {

      e.preventDefault();

      this.focusedIdx--;
      if (this.focusedIdx < 0)
        this.focusedIdx = this.focusedIdx + this.buttons.length;

      break;
    }

    case VK_DOWN:
    case VK_RIGHT: {

      e.preventDefault();

      this.focusedIdx = (this.focusedIdx + 1) % this.buttons.length;

      break;
    }

  case VK_SPACE:
      var focusedButton = e.target;
      var idx = this.buttons.indexOf(focusedButton);
      if (idx < 0)
        return;
      this.focusedIdx = idx;
      break;

    default:
      return;
  }

  this.changeFocus();
};

RadioGroup.prototype.handleClick = function(e) {
  var button = e.target;
  var idx = this.buttons.indexOf(button);
  if (idx < 0)
    return;
  this.focusedIdx = idx;
  this.changeFocus();
};

上為監聽器函數

 RadioGroup.prototype.changeFocus = function() {
   // Set the old button to tabindex -1
   this.focusedButton.tabIndex = -1;
   this.focusedButton.removeAttribute("checked");
   this.focusedButton.setAttribute("aria-checked", "false");

   // Set the new button to tabindex 0 and focus it
   this.focusedButton = this.buttons[this.focusedIdx];
   this.focusedButton.tabIndex = 0;
   this.focusedButton.focus();
   this.focusedButton.setAttribute("checked", "");
   this.focusedButton.setAttribute("aria-checked", "true");
 };

 var group1 = new RadioGroup("#group1");

}());

aria-checked這個屬性不用初始化，可以在焦點改變時修改