function filter(keywords, obj, fields) {
    var result = false
    var keywordArray = parseKeywords(keywords)
    var containKeywords = keywordArray.filter(function (keyword) {
      var containFields = fields.filter(function (field) {
        if (!obj.hasOwnProperty(field)) return false
        if (obj[field].toUpperCase().indexOf(keyword) > -1) return true
      })
      if (containFields.length > 0) return true
      return false
    })
    return containKeywords.length === keywordArray.length
  }
Judge if a given post/page/category/tag contains all of the keywords.
@param Object            obj     Object to be weighted
@param Array<String>     fields  Object's fields to find matches