Sorry for the poorly formulated question..
Here is the code:

module.exports.getUserByQuery = function (params, callback) {
  if (params.nationality.length !== 0 && params.languages.length !== 0) {
    User.find(
      {
        age: {
          $gt: params.minAge,
          $lt: params.maxAge,
        },
        nationality: { $in: paramas.nationality},
        languages: { $in: params.languages },
      },
      callback
    );
  } else if (params.nationality.length === 0 && params.languages.length === 0) {
    User.find(
      {
        age: {
          $gt: params.minAge,
          $lt: params.maxAge,
        },
      },
      callback
    );
  } else if (params.nationality.length !== 0 && params.languages.length === 0) {
    User.find(
      {
        age: {
          $gt: params.minAge,
          $lt: params.maxAge,
        },
        nationality: { $in: params.nationality },
      },
      callback
    );
  } else if (params.nationality.length === 0 && params.languages.length !== 0) {
    User.find(
      {
        age: {
          $gt: params.minAge,
          $lt: params.maxAge,
        },
        languages: { $in: params.languages },
      },
      callback
    );
  }
};

Params.nationality and language can be an empty string array if the website user didn't choose a value in the search engine.
Is there a value I could set them to that would make the filter act as if it didn't exist?
I'm basically looking for a way to get rid of the ifs.

CodePudding user response：

I don't think you can completely eliminate the conditions, but you can structure your code to be better manageable like this (for example):

let params = { minAge: 10, maxAge: 12, nationality: [ ], languages: [ ] }

const filterBuilder = function(params) {

    const f1 = {
        age: {
            $gt: params.minAge,
            $lt: params.maxAge
        }
    }
    const f2 = { nationality: { $in: params.nationality } }
    const f3 = { languages: { $in: params.languages } }

    if (params.languages.length !== 0 && params.nationality.length !== 0) {
         Object.assign(f1, f2, f3);
    } else if (params.languages.length !== 0) {
         Object.assign(f1, f3);
    } else if (params.nationality.length !== 0) {
         Object.assign(f1, f2);
    }

    return f1;
}

User.find(filterBuilder(params), callback);