<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="X-UA-Compatible" content="ie=edge" />
<title>Document</title>
<style type="text/css">
.option_show {
display: none;
}
.discount {
width: 70px;
}
</style>
</head>
<body>
<select class="select" name="oyhfd">
<option value="0" selected="selected">请选择</option>
<option class="option" value="1">足球</option>
<option class="option" value="2">篮球</option>
<option class="option" value="3">乒乓球</option>
<option class="option" value="4">网球</option>
</select>
<span style="display:none;" class="option_show">
<input type="text" class="discount" id="" name="" placeholder="其他球类"/>
</span>
</body>
<script src="https://code.jquery.com/jquery-3.1.1.min.js"></script>
<script>
$(".select").on("change", function() {
if($("option:selected", this).val() == 4) {
$(".option_show").show();
} else {
$(".discount").val("");
$(".option_show").hide();
}
});
</script>
</html>
