<form>
<select name="select" onChange="alert(document.forms[0].select.options[selectedIndex].text)">
<option value="1">潮1</option>
<option value="2">潮2</option>
</select>
<input name="a" type="text">
</form>
<select name="select" onChange="alert(document.forms[0].select.options[selectedIndex].text)">
<option value="1">潮1</option>
<option value="2">潮2</option>
</select>
<input name="a" type="text">
</form>
<select name="select" onChange="document.forms[0].a.value=document.forms[0].select.options[selectedIndex].text">
<option value="1">潮1</option>
<option value="2">潮2</option>
</select>
<input name="a" type="text">