JavaScript] checkbox, element 값 얻기

<input class="messageCheckbox" type="checkbox" value="3" name="mailId[]">
<input class="messageCheckbox" type="checkbox" value="1" name="mailId[]">

var checkedValue = null; 
var inputElements = document.getElementsByClassName('messageCheckbox');
for(var i=0; inputElements[i]; ++i){
      if(inputElements[i].checked){
           checkedValue = inputElements[i].value;
           break;
      }
}

2.element 값 얻기

http://www.mungchung.com/xe/lecture/4197