//server.js
const sql = require('mssql');

var sqlQuery = function(config,query){
var res = {complete: '',results: ''};

    var promise = new Promise((resolve,reject)=>{

      var pool = new sql.connect(config, err=>{
        var request = new sql.Request(pool);
        request.query(query,(err,result)=>{
          if(err){

            res.complete="Errors";
            res.results = []
            reject(res);
          }else{

            res.complete="Complete";
            res.results = result;
            resolve(res);
            pool.close();
          }
        });

      });

      pool.on('error',err=>{
        res.complete="ConnectionError";
        res.results = [];
        reject(res);
      })

    });

    return promise;

}

module.exports.sqlQuery = sqlQuery;

//other.js
var sql = require('./server.js');
var config = {
  server: 'serverIp\\instancia',
  database: "mydb",
  user: "myuser",
  password: "mypass",
  port: 1433
}
var query = "select * from mytable where myfield=somevalue";

var promise = sql.sqlQuery(config,query);
promise.then(result=>{console.log(result)},err=>{console.log("error",err)})