How to determine if a javascript was already loaded by other html file

Question

How to determine if a javascript was already loaded by other html file? I want to reduce the redundant loading of the javascript files to decrease the loading time of my webpage

Answer 1

As Rory says the second request will probably be cached, and noting that this is a bit of a design failure if it can happen, you can understand that the cached file is still going to execute with negative effect.

This is horrible, but you could wrap your JS script like this:

if (!document.foo)
{
  //your script here

  document.foo = true;
}