javascript check if string is number
// native returns true if the variable does NOT contain a valid number
isNaN(num)
// can be wrapped for making simple and readable
function isNumeric(num){
  return !isNaN(num)
}
isNumeric(123)         // true
isNumeric('123')       // true
isNumeric('1e10000')   // true (This translates to Infinity, which is a number)
isNumeric('foo')       // false
isNumeric('10px')      // false
