[제이쿼리] 체크박스 선택한거 -->값,값,값 형태로 만드는 방법

<form name="form">

<table width="100%">
<tr>
 <td><input type="checkbox" name="select1_option" id="select1_option1" class='select1_option' value="a" onClick="test()"> <label for="select1_option1">상품1<font color='#757575'>[1,000원]</font></label></td>
</tr>
<tr>
 <td><input type="checkbox" name="select1_option" id="select1_option2" class='select1_option' value="b" onClick="test()"> <label for="select1_option2">상품2<font color='#757575'>[1,000원]</font></label></td>
</tr>
</table>


<table width="100%">
<tr>
 <td><input type="checkbox" name="select2_option" id="select2_option1" class='select2_option'  value="c" onClick="test()"> <label for="select2_option1">바이럴1<font color='#757575'>[100원]</font></label></td>
</tr>
<tr>
 <td><input type="checkbox" name="select2_option" id="select2_option2" class='select2_option'  value="d" onClick="test()"> <label for="select2_option2">바이럴2<font color='#757575'>[200원]</font></label></td>
</tr>
<tr>
 <td><input type="checkbox" name="select2_option" id="select2_option3" class='select2_option'  value="e" onClick="test()"> <label for="select2_option3">바이럴3<font color='#757575'>[300원]</font></label></td>
</tr>
</table>


<input type="text" name="option_all">

</form>


<script>
function test(){

 form.option_all.value = 체크한 값  b,c,e 이런형태로..
}
</script>