The code below is one of the middlewares in my application, and what it does is that when a user send post request to the server, it saves the form data to engines table and then loads all related engines data to extract average values to insert new data to the corresponding rocket in rockets table. Although it works, apparently my code is so unnecessarily nested(I think) and verbose since I am not familiar with promises..
- How could I write better code or at least simplify a little from it?
- One thing I don't understand from the code is in the comment line.
- Thank you.
const express = require('express');
const app = express();
const logger = require('morgan');
const knex = require('./db/index.js');
const bodyParser = require('body-parser');
const { check, validationResult, body } = require('express-validator/check')
app.use(logger(':method :url :status :date[clf]'));
app.use(express.static("public"));
app.use(bodyParser.json());
app.post('/engines/:id', (req, res) => {
knex('engines').insert({
rocket_id: req.params.id,
user_id: 1,
price: req.body.price,
shining: req.body.shining,
texture: req.body.texture,
modern: req.body.modern,
hardness: req.body.hardness,
loud: req.body.loud,
power: req.body.power,
explosion_risk: req.body.explosion_risk
}).then( () => {
const rocket_temp = {};
return rocket_temp;
}).then( rocket_temp => {
const knexWhere = knex('engines').where({rocket_id: req.params.id});
knexWhere.first().count('explosion_risk').then( data => {
rocket_temp.total_count_risk = data.count;
return rocket_temp;
}).then( rocket_temp => {
knexWhere.where({explosion_risk: true}).first().count('explosion_risk').then( data => {
rocket_temp.countTrue = data.count;
return rocket_temp;
}).then( rocket_temp => {
const knexWhere = knex('engines').where({rocket_id: req.params.id}); // I don't get why knexWhere variable must be re-assigned at this point. Otherwise it won't know that it should load data from 'evaluations' table. Simply saying, the value assigned to knexWhere variable is suddenly changed from this point.(Somehow it loads data from rockets table).
knexWhere.first(knex.raw('ROUND(AVG(price))')).then( data => {
rocket_temp.avg_price = data.round;
return rocket_temp;
}).then( rocket_temp => {
knexWhere.first(knex.raw('ROUND(AVG(shining))')).then( data => {
rocket_temp.avg_shining = data.round;
return rocket_temp;
}).then( rocket_temp => {
knexWhere.first(knex.raw('ROUND(AVG(texture))')).then( data => {
rocket_temp.avg_texture = data.round;
return rocket_temp;
}).then( rocket_temp => {
knexWhere.first(knex.raw('ROUND(AVG(modern))')).then( data => {
rocket_temp.avg_modern = data.round;
return rocket_temp;
}).then( rocket_temp => {
knexWhere.first(knex.raw('ROUND(AVG(hardness))')).then( data => {
rocket_temp.avg_hardness = data.round;
return rocket_temp;
}).then( rocket_temp => {
knexWhere.first(knex.raw('ROUND(AVG(loud))')).then( data => {
rocket_temp.avg_loud = data.round;
return rocket_temp;
}).then( rocket_temp => {
knexWhere.first(knex.raw('ROUND(AVG(power))')).then( data => {
rocket_temp.avg_power = data.round;
return rocket_temp;
}).then( rocket_temp => {
knex('rockets').where({id: req.params.id}).first().update({
price: rocket_temp.avg_price,
shining: rocket_temp.avg_shining,
texture: rocket_temp.avg_texture,
modern: rocket_temp.avg_modern,
hardness: rocket_temp.avg_hardness,
loud: rocket_temp.avg_loud,
power: rocket_temp.avg_power,
explosion_risk: Math.round(parseInt(rocket_temp.countTrue)/parseInt(rocket_temp.total_count_risk) * 100)
}).then( res => {
knex('rockets').select().then( res => console.log(res) )
})
})
})
})
})
})
})
})
})
})
}).then( result => res.sendStatus(201) );
})
