JS文本获得焦点清除文本文字的示例代码

如下所示：
复制代码代码如下:
<！DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
.clearFieldBlurred{
    color:#ccc;
    font-style:italic;
    font-weight:normal;
    width:150px;
}

.clearFieldActive{
    color:#4e4e4e;
    font-weight:bold;
    width:150px;
}
</style>
<script type="text/javascript">
function clearFiled（）{
    var bbb=document.getElementById（"bbb"）;
    if（bbb.value=="bbb"）{
        bbb.value="";
        bbb.className="clearFieldActive";
    }
}

window.document.onmousedown=function（）{
    var bbb=document.getElementById（"bbb"）;
    if（bbb.value==""）{
    bbb.value="bbb";
    bbb.className="clearFieldBlurred";
    }
}
</script>
</head>