代码如下。setTimeout的js语句，如果单独拿出来执行是对的，但是放在setTimeout中就会报错：n is not defined
<head>
<script type="text/javascript">
function timed() {
var n = 0;
for (n = 1; n <= 5; n++) {
setTimeout("document.getElementById('txt').value = "+"n"+" + '秒;'", 1000);
//document.getElementById('txt').value = n + '秒';
}
}
</script>
</head>
<body>
<form>
<input type="button" value="显示计时的文本" onclick="timed()"/>
<input type="text" id="txt"/>
</form>
