javascript验证图片上传的格式和大小

var img = null;
function checkfile(name) {
if (/^.+.(gif|jpg|bmp|swf|jpeg)$/i.test(name)) {
if (img) {
img.removeNode(true);
}
img = document.createElement("img");
img.style.display = "none";
img.attachEvent("onreadystatechange", orsc);
document.body.insertAdjacentElement("beforeend", img);
img.src = name;
} else {
oe();
}
}
function oe() {
uploadAFileForm.reset();
alert("上传文件的格式只能是 <gif><jpg><jpeg><swf>!");
}
function orsc() {
if (img.fileSize > 716800) {
uploadAFileForm.reset();
alert("上传文件的大小不能超过700K!");
}
}