how to get numbers only while entering characters in javascript

You can use jQuery validation .......

I think you're asking: how to get only the numeric characters out of a string, ignoring everything else. You could use a regex and then stick all the matches together, but that seems like overkill when you can process it character by character easily enough:

string NumbersOnly(string input){
 StringBuilder output = new StringBuilder();
 foreach(char c in input)
  if(c >= '0' && c <= '9') output.Append(c);
 return output.ToString();
}

if your input is (123)(12345)
then you can use split properties of the string...
eg.

string num =(123)(12345);

now you can split it into two half..

string[] newnum = num.Split('(');

now you get newnum[0]=123)
and next is newnum[1]=12345)
again you can use for loop next to omit ')'

string fnum;
string snum;
for(int i = 0; i < newnum.Length; i++)
{
   if(i==0)
   {
      string[] num = newnum[i].Split(')');
      fnum = num[0];
      //here fnum = 123
   }
   
   else if(i==1)
   {
      string[] num = newnum[i].Split(')');
      snum = num[1];
      //here snum = 12345;
   }
}

Thus, you can use 'SPLIT' to split the string....