js判断字符串是否是数字

function isnumericvalid(bwrnumber)
{

 var validchars = "0123456789";
 var isnumber=true;
 var char;
 
    for (i = 0; i < bwrnumber.length && isnumber == true; i++)
 {
  char = bwrnumber.charat(i);
  if (validchars.indexof(char) == -1)
  {
   isnumber = false;
  }
 }
 return isnumber;
}