javascript cant access variable inside function code example

Example 1: javascript function call with variable

function abc() {
  alert('test');
}

var funcName = 'abc';

window[funcName]();

Example 2: variable used in a function can be used in another function js

function medium(){
         var user1=new collector(one,two);
         var user2=new collector(one,two);
         login(user1,user2);

       }

      function login(user1,user2){
        var u1=user1.username;
        var u12=user1.password;
        var u2=user2.username;
        var u22=user2.password;
      }