用jquery通过点击事件把下拉列表币种的值传给文本框1，再通过文本框1的币种名称用if转化为币别传值给文本框2保存
<script src="https://cdn.staticfile.org/jquery/2.2.4/jquery.min.js"></script>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>文档标题</title>
<script src="https://lib.sinaapp.com/js/jquery/1.9.1/jquery- 1.9.1.min.js"></script>
</head>
<body>
<h1>我的第一个HTML页面</h1>
<p )}
}
</script>
</body>
</html>
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展示
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