找input 的　id=”test”
https://js.do/powenko/01-find-input-id

[javascript]
<script src="//ajax.googleapis.com/ajax/libs/jquery/3.1.0/jquery.min.js"></script>

<input id="test1" list="values" placeholder="select">
<datalist id="values">
<option value="orange">
<option value="banana">
<option value="lemon">
<option value="apple">
</datalist>
<script>
$(‘input #test1’).on(‘click’, function() {
$(this).attr(‘placeholder’,$(this).val());
$(this).val(”);
});
$(‘input #test1’).on(‘mouseleave’, function() {
if ($(this).val() == ”) {
$(this).val($(this).attr(‘placeholder’));
}
});
</script>
<!– edit your html here –>

[/javascript]