gistfile1.js

  include: {  
    is: ['string', 'array', 'regexp', 'object'],
    ok: (rule) => {
      
      function checkURL(r) {
        if (isRegExpOrString(r))
          return true;
        if (Array.isArray(r) && r.length > 0)
          return r.every(isRegExpOrString);
        return false;
      }

      function checkContentType(r) {
        if (typeof r === 'string')
          return true;
        if (Array.isArray(r) && r.length > 0)
          return r.every((v) => typeof v === 'string')
        return false;
      }

      // If rule is an object check url and contentType
      if (typeof rule === 'object') {
        if (rule.url && rule.contentType) {
          if (checkURL(rule.url) && checkContentType(rule.contentType)) {
            return true;
          }
          return false;
        }
        return false;
      }
      else {
        if (checkURL(rule))
          return true;
        return false;
      }
    },
    msg: 'The `include` option must always contain atleast one rule as a string, regular expression, or an array of strings and regular expressions.'
  },