js实现上传文件扩展名小写转换

<form name=form>

<input name=jts value="" size=10>

<input type="file" name=upf onchange="ty()";>

</form>

<script>

function ty(){

var srcc = document.form.upf.value;

srcc = srcc.toString()

start = srcc.indexOf(".");

end = srcc.length;

ts=srcc.substring(start+1,end);

//swordmaple javascript article.

nts=ts.toLowerCase();

document.form.jts.value=nts;

alert("你选择的文件类型是"+document.form.jts.value+"!");

}

</script>