code: function isValidJSONPointer(pointer) {
      // Validates JSON pointer string.
  
      if (!isString(pointer)) {
        // If it's not a string, it obviously is not valid.
        return false;
      }
  
      if ('' === pointer) {
        // If it is string and is an empty string, it's valid.
        return true;
      }
  
      // If it is non-empty string, it must match spec defined format.
      // Check Section 3 of specification for concrete syntax.
      return NON_EMPTY_POINTER_REGEXP.test(pointer);
    }
docs: Returns true if given |pointer| is valid, returns false otherwise.
  @param {!string} pointer
  @returns {boolean} Whether pointer is valid.