Recommended way to check file size on upload

Question

I am working on a web application which supports file uploading. I am already familiar checking the size in server side, but i wanted to check the file size in a client side.

Answer 1

In IE, you can do it with JS and ActiveX:

function A()
{
  var oas = new ActiveXObject("Scripting.FileSystemObject");
  var d = document.a.b.value;
  var e = oas.getFile(d);
  var f = e.size;
  alert(f + " bytes");
}