javascript - 仅在文件上传完成后执行函数。Javascript

Question

如何（通过使用javascript）仅在文件上传完成后才执行函数？我的意思是 'uploading2' 仅在 'submit()' 完成后执行。

function uploadimg1() {
  document.forms.imgupload.act.value='upload';
  document.forms.imgupload.submit();
}
function uploadimg2() {
  doc = frames['frm1'].document;
  imgs=doc.getElementsByTagName('img').length-1;
  img = doc.getElementById(imgs);
  opener.document.forms[0].src.value = '<?php echo $IMGURL ?>/'+img.alt;
  window.close();
}
function uploadimg() {
  uploadimg1();
  uploadimg2();
}