select how to select multiple values

1. Code:

   <select>
   <option value>请选择...</option>
   </select>
   <script>
   var $arr = [
       {name:'lee',sex:'male'},
       {name:'zhangsan',sex:'femal'}
   ]
   var select = document.getElementsByTagName('select')[0]
   function render(arr){
       var str = ''
       for(var i in arr){
           var name = arr[i]['name']
           var sex = arr[i]['sex']
           str += "<option value='"+name+";"+sex+"'>"+name+"</option>"
       }
       select.innerHTML += str
   }
   select.onchange = render($arr)
   </script>

2. Effect: