can anyone help me fix this webpage and make it work ? by html and js

i can log in to the webpage by username"user 1 "password "12345678"

i have write code like this

main .html:

user login
user
pa ss wo rd

1:js

function check() {

var user_name=form1.user.value;

var user_pwd=form1.pwd.value;

if((user_name=="")||(user_name==null)){

alert("enter username");

form1.user.focus();/

return;

}

else if((user_name=="user1")|){

alert("enter password");

form1.user.focus();/

return;

}

else if((user_pwd=="")||(user_pwd==null))

alert("enter password ");

form1.pwd.focus();

return;}

else if{((user_pwd=="12345678")!

form1.submit();

window.open( 21.html");

}

}

i want to make to show a login page ,and i can enter password and username to log in ,i log in ,will gho to 2 .html ,and the heml webpage will show "you have successfully log in .

if not ,will show "wong paword or wrong username .'can anyone help fix this code ?

ty