Sys.ScriptLoadFailedException: .js file cannot load

We cannot access External .js files directly in UpdatePanel. If you tries to access then you will get below
error

Error : Sys.ScriptLoadFailedException: .js file cannot load

To resolve this issue, we need to add below line of code at the end of  .js file

if (typeof (Sys) != "undefined")

 { if (typeof (Sys.Application) != "undefined") { Sys.Application.notifyScriptLoaded(); } }