SOURCE

function getNum(str) 
{
var num = 0;
for (var i = 0; i < str.length; i++) 
    {
var char = str.charAt(i);
if (char != " " && !isNaN(char)) 
        {
num++;
        }
    }
return num;
}
document.write(getNum("12sdf983jkdsa23"));