Using java script How to validate the password in asp.net c#

function CheckPassword()
       {
           var password = document.getElementById('<%=txtPassword.ClientID %>').value;
           var txtPassword = document.getElementById('<%=lblPasswordMeter.ClientID %>');

           var score = 0;

           if(password.length < 8)
           {
               //this is a very weak password
               txtPassword.style.color = "Red";
               txtPassword.innerHTML = "Too short";
               return;

           }

           //lets check for small letters
           for(var s=0; s<password.length; ++s)
           {
               if(password.charCodeAt(s) >= 'a'.charCodeAt(0) && password.charCodeAt(s) <= 'z'.charCodeAt(0))
               {
                   score += 1;
                   break;
               }
           }

           //lets check for capital letters
           for(var s=0; s<password.length; ++s)
           {
               if(password.charCodeAt(s) >= 'A'.charCodeAt(0) && password.charCodeAt(s) <= 'Z'.charCodeAt(0))
               {
                   score += 1;
                   break;
               }
           }

           //Lets check for numbers
           for(var s=0; s<password.length; ++s)
           {
               if(password.charCodeAt(s) >= '0'.charCodeAt(0) && password.charCodeAt(s) <= '9'.charCodeAt(0))
               {
                   score += 1;
                   break;
               }
           }

          //lets now calculate final score to declare the results
          switch(score)
          {
           case 0:
           case 1:
               txtPassword.style.color = "Red";
               txtPassword.innerHTML = "too weak";
           break;
           case 2:
               txtPassword.style.color = "Orange";
               txtPassword.innerHTML = "average";
           break;
           case 3:
               txtPassword.style.color = "Green";
               txtPassword.innerHTML = "strong";
           break;
          }
       };