mongodbrelation/index.js

ONE_TO_MANY, MANY_TO_ONE, ONE_TO_ONE, MANY_TO_MANY realtionships among diffrent collections in mongodb

const JOIN_TYPE_ENUM = {
    ONE_TO_ONE: 1,
    ONE_TO_MANY: 2,
    MANY_TO_MANY: 3,
    MANY_TO_ONE: 4
}
module.exports = {
  joinedQuery : function (condition,joinCollectionName, joinFieldName, foreignFieldName, aliasname, outputfields, typeofJoin) {
      let error = null;
      if (!joinCollectionName && !joinFieldName && !foreignFieldName && !outputfields && !typeofJoin) {
          error = new Error();
          error.name = 'invalid input';
          error.message = "please pass mandatory fields";
      }
      if (!JOIN_TYPE_ENUM.hasOwnProperty(typeofJoin)){
          error = new Error();
          error.name = 'invalid input';
          error.message = "please pass proper typeofJoin";
      }
      if (error) {
          throw error;
          return 0;
      }
      let query = [];
      let lookupparentjson = {$lookup: null};
      let lookupjson = {from: '', localField: '', foreignField: '', as: '' };
      let unwindparentjson = {$unwind: null};
      let projectparentjson = {$project: null};
      if (condition) {
          let matchparentjson = {$match: null};
          matchparentjson.$match = condition;
          query.push(matchparentjson);
      }
      try {
          switch (JOIN_TYPE_ENUM[typeofJoin]) {
              case 1:
                  lookupjson.from = joinCollectionName;
                  lookupjson.localField = joinFieldName;
                  lookupjson.foreignField = foreignFieldName;
                  lookupjson.as = aliasname;
                  lookupparentjson.$lookup = lookupjson;
                  query.push(lookupparentjson);
                  unwindparentjson.$unwind = '$'+aliasname;
                  query.push(unwindparentjson);
                  break;
              case 2:
                  lookupjson.from = joinCollectionName;
                  lookupjson.localField = joinFieldName;
                  lookupjson.foreignField = foreignFieldName;
                  lookupjson.as = aliasname;
                  lookupparentjson.$lookup = lookupjson;
                  query.push(lookupparentjson);
                  // unwindparentjson.$unwind = '$'+aliasname;
                  // query.push(unwindparentjson);
                  break;
              case 3:
                  lookupjson.from = joinCollectionName;
                  lookupjson.localField = joinFieldName;
                  lookupjson.foreignField = foreignFieldName;
                  lookupjson.as = aliasname;
                  lookupparentjson.$lookup = lookupjson;
                  query.push(lookupparentjson);
                  break;
              case 4:
                  lookupjson.from = joinCollectionName;
                  lookupjson.localField = joinFieldName;
                  lookupjson.foreignField = foreignFieldName;
                  lookupjson.as = aliasname;
                  lookupparentjson.$lookup = lookupjson;
                  query.push(lookupparentjson);
                  unwindparentjson.$unwind = '$'+aliasname;
                  query.push(unwindparentjson);
                  break;
          }
          if (outputfields) {
              projectparentjson.$project = outputfields;
              query.push(projectparentjson)
          }
      // push look up
      // push unwind if applicable
      // push project fields
      return query;
      } catch (e) {
          throw e;
          return 0;
      }
  }
}