Hope this will help.

rem Use %SendKeys% to send keys to the keyboard buffer
set SendKeys=CScript //nologo //E:JScript "%~F0"

rem wait for the browser to finish loading
timeout /t 10

%SendKeys% "your_username"
%SendKeys% "{TAB}"
%SendKeys% "your_password"
%SendKeys% "{ENTER}"

goto:EOF

@end
// JScript section

var WshShell = WScript.CreateObject("WScript.Shell");
WshShell.SendKeys(WScript.Arguments(0));

source:https://stackoverflow.com/questions/29403376/automatically-open-a-browser-and-login-to-a-site

Hope this will help.

rem Use %SendKeys% to send keys to the keyboard buffer
set SendKeys=CScript //nologo //E:JScript "%~F0"

rem wait for the browser to finish loading
timeout /t 10

%SendKeys% "your_username"
%SendKeys% "{TAB}"
%SendKeys% "your_password"
%SendKeys% "{ENTER}"

goto:EOF

@end
// JScript section

var WshShell = WScript.CreateObject("WScript.Shell");
WshShell.SendKeys(WScript.Arguments(0));

thanks to @Varun_ved

source:https://stackoverflow.com/questions/29403376/automatically-open-a-browser-and-login-to-a-site