javascript show hidden div when select option is selected

參考來源:javascript show hidden div when select option is selected
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<select id="test" name="form_select" onchange="showDiv(this)">
   <option value="0">No</option>
   <option value ="1">Yes</option>
</select>
<div id="hidden_div" style="display: none;">Hello hidden content</div>
function showDiv(elem){
   if(elem.value == 1)
      document.getElementById('hidden_div').style.display = "block";
}