isNumber = function isNumber(val) {
  var type = typeof val;
  return type === 'number' || (type === 'object' && objToString.call(val) === '[object Number]');
}
Tests if a value is a number.

@name isNumber
@api private
@param {*} val The value to test.
@return {boolean} Returns `true` if `val` is a number, otherwise `false`.