'Can not read property' length 'of undefined' nodeJS

res.render is being called before the promise of sql.connect is resolved and also the variable articulos is not declared in the same scope as the call to res.render .

Remember that all code within the .then callback is asynchronous.

The proposed solution is to move the lines:

sql.close();
res.render('menu/analisisDetallado', { ListArticulos: articulos });

within the call to .then of request.query

{
    getAnalisisDetallado: function(req, res, next) {

        var config = require('.././database/config');

        sql.connect(config)
            .then(function () {
                var articulos = null;
                var request = new sql.Request();
                request.query("SELECT TOP 10  SI_Id_Inventario, SI_Articulo, SI_UM, SI_Ubicacion FROM SI_Inventario_Teorico_QAD")
                    .then(function (result) {
                        articulos = result.recordset || [];
                        console.log('Recordset: ' + result.recordset);
                        console.log('Affected: ' + request.rowsAffected);
                        sql.close();
                        res.render('menu/analisisDetallado', { ListArticulos: articulos });
                    })
                    .catch(function(err) {
                        console.log('Request error: ' + err);
                    });
            })
            .catch(function (err) {
                if (err) {
                    console.log('SQL Connection Error: ' + err);
                }
            });
    }
}

I think the problem is here:

// quito el request.query porque el formato queda poco legible
.then(function(err, rows, recordset) {
                if (err) console.log(err)
                articulos = rows;
                ....

The problem is that, if you fail the promise that you're calling, anyway you call

res.render('menu/analisisDetallado', { ListArticulos: articulos });

You have to find a way to guarantee (in case you have to always call it) that articles have an array.

 articulos = rows || [];

The above code should work for you. If rows comes undefined or null then you assign an empty array.

EDITED

The error with Promise comes up because you do not handle the failed results. I give you an example

var articulo = []
then(function () {
     console.log("Aqui fue bien");
     articulo = rows
}).catch(function () {
     console.log("Aqui fue mal");
});

res.render('menu/analisisDetallado', { ListArticulos: articulos });

According to the mssql library, in its 4.x version you can use asynchronous functions, for this you need nodejs or higher:

getAnalysisDetailed (data)

const sql = require('mssql');
const config = require('../../database/config');

const getAnalisisDetallado = async function () {
  try {
    await sql.connect();
    const request = new sql.Request();
    const articulos = request.query'SELECT TOP 10  SI_Id_Inventario, SI_Articulo, SI_UM, SI_Ubicacion FROM SI_Inventario_Teorico_QAD';
    return articulos;
  } catch(e) {
    throw new Error(e.message);
  }
}

getAnalysisDetailed (handler)

getAnalasisDetallado = (req, res) => {
  getAnalisisDetallado()
    .then(articulos => {
      res.render('menu/analisisDetallado', { ListaArticulos: articulos });
    })
    .catch(err => {
      res.render('menu/analisisDetallado', { ListaArticulos: [], error: err });
    });
}

In the 3.x version, you can use any old version ( nodejs 4.x +), since there is no support for asynchronous functions:

const getAnalisisDetallado = async function () {
  return (
    sql
      .connect()
      .then((resolve, reject) => {
        const request = new sql.Request();
        request
          .query('SELECT TOP 10  SI_Id_Inventario, SI_Articulo, SI_UM, SI_Ubicacion FROM SI_Inventario_Teorico_QAD')
          .then((err, rows, recorset) => {
            if (err) { reject(err.message); }
            resolve(rows);
          });
      })
  );
}