In my programming in Node.JS I made some code that worked, but I want to understand the concept of how it works.
In the code in question I use knex to retrieve information from a MySQL database. I import the knex module for that:
const config = {...}
const knex = require('knex')(config)
So far nothing new, only this time I needed to do a nested query and it was the first time. In this case, I consulted the sales data and then the sale items. I did it as follows:
const getSales = async () => {
await knex("tbl_vendas")
.select(knex.raw("tbl_vendas.id_vendas, tbl_vendedores.nome AS vendedor, " +
"tbl_clientes.nome_razaosocial AS cliente, tbl_vendas.data, tbl_vendas.hora, " +
"tbl_vendas.cupom, tbl_vendas.total"))
.leftOuterJoin("tbl_vendedores", "tbl_vendedores.id_vendedores", "tbl_vendas.id_vendedores")
.leftOuterJoin("tbl_clientes", "tbl_clientes.id_clientes", "tbl_vendas.id_clientes")
.then(sales => {
const rows = sales.map(sale => {
return knex("tbl_vendas_itens")
.select("tbl_vendas_itens.id_vendas_itens AS id_item", "tbl_produtos.descricao",
"tbl_vendas_itens.qtde", "tbl_vendas_itens.vl_unitario", "tbl_vendas_itens.desconto",
"tbl_vendas_itens.vl_total")
.leftOuterJoin("tbl_produtos", "tbl_vendas_itens.id_produtos", "tbl_produtos.id_produtos")
.where("tbl_vendas_itens.id_vendas", "=", sale.id_vendas)
.then(sales_items => {
const newRow = { ...sale, itens: [...sales_items] }
return newRow
})
})
return Promise.all(rows)
})
.then(console.log);
}
Writing this code was pretty intuitive and it worked, but then I was amazed that I used the knex constant twice, one inside the other, and it didn't hurt.
I ran a console.log(typeof(knex)) to find out what it was and it returned that it is a function.
Could someone explain the theory behind the use of knex inside the other and help me understand why it is okay to do this?
Related
I'm trying to update a column in my PostgresQL database using Nodejs:
res.rows.forEach((tmdbID) => {
(async () => {
const json = await fetchMovieData(tmdbID.tmdb_id);
const overview = json.overview.replace('\'', '\\\'');
console.log(overview);
pool.query(`UPDATE "Movie" SET overview = '${overview}' WHERE tmdb_id = ${json.id}`);
})();
});
async function fetchMovieData(tmdbID) {
const response = await fetch(`https://api.themoviedb.org/3/movie/${tmdbID}?api_key=a8f7039633f2065942cd8a28d7cadad4&language=en-US`);
const data = response.json();
return data;
}
The error I'm getting:
(node:1412) UnhandledPromiseRejectionWarning: error: syntax error at or near "s"
It happens on this string:
The Bride unwaveringly continues on her roaring rampage of revenge against the band of assassins who had tried to kill her and her unborn child. She visits each of her former associates one-by-one, checking off the victims on her Death List Five until there \'s nothing left to do … but kill Bill.
I'm trying to escape the 'but it doesn't seem to be working. Any tips?
Don't try to pass everything as a String, that is how SQL Injection happens. A better approach is to use parameters.
I'm not exactly sure which library are you using, but the syntax should be something similar to this:
pool.query('UPDATE "Movie" SET overview = ? WHERE tmdb_id = ?', [overview, json.id]);
I’m trying to read the sentiment of multiple Reddit posts. I’ve got the idea to work using 6 API calls but I think we can refactor it to 2 calls.
The wall I’m hitting - is it possible to loop through multiple APIs (one loop for each Reddit post we’re scrapping), print the results, and then add them into a single variable?
The last part is where I’m stuck. After looping through the API, I get separate outputs for each loop and I don’t know how to add them into a single variable…
Here’s a simple version of what the code looks like:
import React, { useState, useEffect } from 'react';
function App() {
const [testRedditComments, setTestRedditComments] = useState([]);
const URLs = [
'https://www.reddit.com/r/SEO/comments/tepprk/is_ahrefs_worth_it/',
'https://www.reddit.com/r/juststart/comments/jvs0d1/is_ahrefs_worth_it_with_these_features/',
];
useEffect(() => {
URLs.forEach((URL) => {
fetch(URL + '.json').then((res) => {
res.json().then((data) => {
if (data != null) setTestRedditComments(data[1].data.children);
});
});
});
}, []);
//This below finds the reddit comments and puts them into an array
const testCommentsArr = testRedditComments.map(
(comments) => comments.data.body
);
//This below takes the reddit comments and terns them into a string.
const testCommentsArrToString = testCommentsArr.join(' ');
console.log(testCommentsArrToString);
I've tried multiple approaches to adding the strings together but I've sunk a bunch of time. Anyone know how this works. Or is there a simpler way to accomplish this?
Thanks for your time and if you need any clarification let me know.
-Josh
const URLs = [
"https://www.reddit.com/r/SEO/comments/tepprk/is_ahrefs_worth_it/",
"https://www.reddit.com/r/juststart/comments/jvs0d1/is_ahrefs_worth_it_with_these_features/",
];
Promise.all(
URLs.map(async (url) => {
const resp = await fetch(url + ".json");
return resp.json();
})
).then((res) => console.log(res));
I have used Promise.all and got the response and attached a react sandbox with the same.
Based on your requirements, you can use state value or you can prepare your api response before setting it to state.
Background: Been trying for the last 2 day to resolve this myself by looking at various examples from both this website and others and I'm still not getting it. Whenever I try adding callbacks or async/await I'm getting no where. I know this is where my problem is but I can't resolve it myself.
I'm not from a programming background :( Im sure its a quick fix for the average programmer, I am well below that level.
When I console.log(final) within the 'ready' block it works as it should, when I escape that block the output is 'undefined' if console.log(final) -or- Get req/server info, if I use console.log(ready)
const request = require('request');
const ready =
// I know 'request' is deprecated, but given my struggle with async/await (+ callbacks) in general, when I tried switching to axios I found it more confusing.
request({url: 'https://www.website.com', json: true}, function(err, res, returnedData) {
if (err) {
throw err;
}
var filter = returnedData.result.map(entry => entry.instrument_name);
var str = filter.toString();
var addToStr = str.split(",").map(function(a) { return `"trades.` + a + `.raw", `; }).join("");
var neater = addToStr.substr(0, addToStr.length-2);
var final = "[" + neater + "]";
// * * * Below works here but not outside this block* * *
// console.log(final);
});
// console.log(final);
// returns 'final is not defined'
console.log(ready);
// returns server info of GET req endpoint. This is as it is returning before actually returning the data. Not done as async.
module.exports = ready;
Below is an short example of the JSON that is returned by website.com. The actual call has 200+ 'result' objects.
What Im ultimately trying to achieve is
1) return all values of "instrument_name"
2) perform some manipulations (adding 'trades.' to the beginning of each value and '.raw' to the end of each value.
3) place these manipulations into an array.
["trades.BTC-26JUN20-8000-C.raw","trades.BTC-25SEP20-8000-C.raw"]
4) export/send this array to another file.
5) The array will be used as part of another request used in a websocket connection. The array cannot be hardcoded into this new request as the values of the array change daily.
{
"jsonrpc": "2.0",
"result": [
{
"kind": "option",
"is_active": true,
"instrument_name": "26JUN20-8000-C",
"expiration_timestamp": 1593158400000,
"creation_timestamp": 1575305837000,
"contract_size": 1,
},
{
"kind": "option",
"is_active": true,
"instrument_name": "25SEP20-8000-C",
"expiration_timestamp": 1601020800000,
"creation_timestamp": 1569484801000,
"contract_size": 1,
}
],
"usIn": 1591185090022084,
"usOut": 1591185090025382,
"usDiff": 3298,
"testnet": true
}
Looking your code we find two problems related to final and ready variables. The first one is that you're trying to console.log(final) out of its scope.
The second problem is that request doesn't immediately return the result of your API request. The reason is pretty simple, you're doing an asynchronous operation, and the result will only be returned by your callback. Your ready variable is just the reference to your request object.
I'm not sure about what is the context of your code and why you want to module.exports ready variable, but I suppose you want to export the result. If that's the case, I suggest you to return an async function which returns the response data instead of your request variable. This way you can control how to handle your response outside the module.
You can use the integrated fetch api instead of the deprecated request. I changed your code so that your component exports an asynchronous function called fetchData, which you can import somewhere and execute. It will return the result, updated with your logic:
module.exports = {
fetchData: async function fetchData() {
try {
const returnedData = await fetch({
url: "https://www.website.com/",
json: true
});
var ready = returnedData.result.map(entry => entry.instrument_name);
var str = filter.toString();
var addToStr = str
.split(",")
.map(function(a) {
return `"trades.` + a + `.raw", `;
})
.join("");
var neater = addToStr.substr(0, addToStr.length - 2);
return "[" + neater + "]";
} catch (error) {
console.error(error);
}
}
}
I hope this helps, otherwise please share more of your code. Much depends on where you want to display the fetched data. Also, how you take care of the loading and error states.
EDIT:
I can't get responses from this website, because you need an account as well as credentials for the api. Judging your code and your questions:
1) return all values of "instrument_name"
Your map function works:
var filter = returnedData.result.map(entry => entry.instrument_name);
2)perform some manipulations (adding 'trades.' to the beginning of each value and '.raw' to the end of each value.
3) place these manipulations into an array. ["trades.BTC-26JUN20-8000-C.raw","trades.BTC-25SEP20-8000-C.raw"]
This can be done using this function
const manipulatedData = filter.map(val => `trades.${val}.raw`);
You can now use manipulatedData in your next request. Being able to export this variable, depends on the component you use it in. To be honest, it sounds easier to me not to split this logic into two separate components - regarding the websocket -.
I am very new to Firebase and JS itself as well, and it is not the easiest thing to understand.
So, I have a Firebase real time databse set up with dummy "users" profiles, that each contain different properties.
i am trying to call user's properties.
I have managed to achieved it with the following approach:
let installDateRef = database.ref(`users/${userAccount}/installationDate`);
let lastUsedDateRef = database.ref(`users/${userAccount}/lastUsed`);
installDateRef.on('value', function(snapshot) {
installationDate.innerText = (snapshot.val());
}, function (error) {
installationDate.innerText = `Error: ${error.code}`
});
lastUsedDateRef.on('value', function(snapshot) {
lastUsedDate.innerText = (snapshot.val());
}, function (error) {
lastUsedDate.innerText = `Error: ${error.code}`
});
But in my application I want to display all of the user information, so copying this ".on" function seems like overkill.
Someone said that there is cleaner approach like this below
const firebasePromises = [
database.ref(`users/${userAccount}/installationDate`),
database.ref(`users/${userAccount}/lastUsed`)
];
Promise.all(firebasePromises).then(([_installationDate, _lastUsed]) => {
installationDate.innerText = (_installationDate.val());
lastUsedDate.innerText = (_lastUsed.val());
})
But I honest to God cannot make it work. It either returns undefined or returns array of my promises const.
.val() does not work at all even, saying that this is not a function.
Any help would on the best and working practice would be soooo much appreciated.
Thank you
#Doug Stevenson thank you! This is exactly what was needed:
const firebasePromises = [
database.ref(`users/${userAccount}/installationDate`).once('value'),
database.ref(`users/${userAccount}/lastUsed`).once('value'),
];
Promise.all(firebasePromises).then(snap => {
installationDateHTML.innerText = snap[0].val();
lastUsedDateHTML.innerText = snap[1].val();
})
I'm starting to learn firebase with firestore.
I have spent more hours than I would've like understanding the reference type and trying to get it to work with a simple query that references a portfolio's category.
This is the code:
try {
const portfolioSnap = await db.collection("portfolio").get();
let portfolioDoc = portfolioSnap.docs;
let categoriesRef = [];
portfolioDoc.forEach(p => {
categoriesRef.push(p.data().category.get());
});
let categories = await Promise.all(categoriesRef);
let portfolio = [];
portfolioDoc.map((p, i) => {
let portfolioObject = {
...p.data(),
category: categories[i].data().name
};
portfolio.push(portfolioObject);
});
return portfolio;
} catch (error) {
console.warn("ERROR: ", error);
}
I'm not sure if this makes sense.
I'm trying to get the category for each portfolio document but I feel this is over-engineered or I'm totally doing it the wrong way.
And this is not counting if I have references for images or files which I feel would make things... well, not pretty.
Nothing strange here. This is the way that nosql databases work (since there is no join operation, nor is there any explicit relationships between documents other than what you define).