The MicrosoftAjax.js has Sys.EventArgs

    Sys.EventArgs = function () { };
    Sys.EventArgs.registerClass("Sys.EventArgs");
    Sys.EventArgs.Empty = new Sys.EventArgs;
    Sys.Res={'....'}
    if(typeof(Sys)!=='undefined')Sys.Application.notifyScriptLoaded();

The javascript file in my project references the MicrosoftAjax.js file and uses Sys.EventArgs like

Root.Context.ContextCompletedEventArgs.registerClass
('Root.Context.ContextCompletedEventArgs', Sys.EventArgs);

Considering MicrosoftAjax.js is very old, I want to remove the reference of the MicrosoftAjax.js file and serve the purpose of Sys.EventArgs in javascript file only. Is there any way I can achieve it ?

Please know that I am primarily a .NET dev and a beginner in javascript. Thanks in advance