I use lowDB dependency to control the JSON Data with Express and actually it works. But there is a bug and I cannot find how to solve it.
I create /create page to add information in JSON file and it contains 4 form and submit button.
And In express I code like this. each forms data will save it in variable and push with lowdb module.
router.post('/post', function (req, res) {
let pjName = req.body.projectName;
let pjURL = req.body.projectURL;
let pjtExplanation = req.body.projectExplanation;
let pjImgURL = req.body.projectImgURL;
console.log(pjName);
db.get('project').push({
name: pjName,
url: pjURL,
explanation: pjtExplanation,
imgurl: pjImgURL
}).write();
console.log(db.get('project'));
console.log(db.get('project').value());
res.redirect('/');
})
And it works well. But when I modify the JSON file myself (ex. reset the JSON file) and execute again. It shows the data that I reset before. I think in this app somewhere saves the all data and show save it in array again.
And When I shutdown the app in CMD and execute again, the Array is initialized.
As you may already know the lowdb persist the data into your secondary memory (hdd), and may return a promise depending on your environment when you call write method.As mentioned in the doc
Persists database using adapter.write (depending on the adapter, may return a promise).
So the data may be still getting write when you read them, so the old data is queried. Try this,
db.get('project').push({
name: pjName,
url: pjURL,
explanation: pjtExplanation,
imgurl: pjImgURL
}).write().then(() => {
console.log(db.get('project'));
console.log(db.get('project').value());
});
Related
I am new to programming, and I heard that some guys on this website are quite angry, but please don't be. I am creating one web app, that has a web page and also makes som ecalculations and works with database (NeDB). I have an index.js
const selects = document.getElementsByClassName("sel");
const arr = ["Yura", "Nairi", "Mher", "Hayko"];
for (let el in selects) {
for (let key in arr) {
selects[el].innerHTML += `<option>${arr[key]}</option>`;
}
}
I have a function which fills the select elements with data from an array.
In other file named: getData.js:
var Datastore = require("nedb");
var users = new Datastore({ filename: "players" });
users.loadDatabase();
const names = [];
users.find({}, function (err, doc) {
for (let key in doc) {
names.push(doc[key].name);
}
});
I have some code that gets data from db and puts it in array. And I need that data to use in the index.js mentioned above, but the problem is that I don't know how to tranfer the data from getData.js to index.js. I have tried module.exports but it is not working, the browser console says that it can't recognize require keyword, I also can't get data directly in index.js because the browse can't recognize the code related to database.
You need to provide a server, which is connected to the Database.
Browser -> Server -> DB
Browser -> Server: Server provides endpoints where the Browser(Client) can fetch data from. https://expressjs.com/en/starter/hello-world.html
Server -> DB: gets the Data out of the Database and can do whatever it want with it. In your case the Data should get provided to the Client.
TODOs
Step 1: set up a server. For example with express.js (google it)
Step 2: learn how to fetch Data from the Browser(Client) AJAX GET are the keywords to google.
Step 3: setup a Database connection from you Server and get your data
Step 4: Do whatever you want with your data.
At first I thought it is a simple method, but them I researched a little bit and realized that I didn't have enough information about how it really works. Now I solved the problem, using promises and templete engine ejs. Thank you all for your time. I appreciate your help)
I've got a simple axios GET request that is working with Azure directline 3.0. The GET request pulls back data and shows it in the console (as seen in the picture).
The data I want to save into a variable is the conversationId. I then want to use this variable with Axios Post in another JS file to post as part of the link e.g. let URL = "https://directline.botframework.com/v3/directline/conversations/"+convID"/activities". With convID being the variable I wish to create. Right now I am manually changing the convID with the new conversation ID, but I want to create a variable so I can place it in the post javascript file so it is automatic.enter image description here
There are various ways you can solve this problem. Easiest one being, exposing the data on a shared object window.convID = convID and then accessing it wherever required.
You could also look to make singleton objects, which can be instantiated only once and hence will share it's variables across the lifespan of the application.
axios.get(/* URL */).then(res => {
window.convID = res.data.conversationId;
});
You can save that variable value in LocalStorage. Something like this:
let routeToYourApi = '/api/conversations'; // or something like this...
axios.get(routeToYourApi).then((response) => {
let conversationId = response.data.conversationId; // not sure if data object from your image is directly nested inside response that you get from server, but you get the idea...
window.localStorage.setItem("convId", conversationId);
}) // here you can fetch your conversation id
Than you can access it anywhere in your app:
let conversationId = window.localStorage.getItem("convId");
... and eventually remove it from local storage:
window.localStorage.removeItem("convId")
Hope this will help you!
So basically I wrote a simple API where you can perform http POST and http GET on a nedb.
My problem however is, that after posting an entry (customer), the entry appears in the nedb file but when I use the GET method it isn't returned.
However after restarting the API it works as expected and the expected data is returned. But why does it have to restart in order to "refresh" the data?
Get-Function:
const db = new Datastore({filename: __dirname + '/db.dat', autoload:true});
export function getAll(req: Request, res:Response, next: Next):void{
db.find({}, (err, customers) => {
res.send(customers);
});
next();
}
In situations where you get weird errors or something strange is not working with nedb and you cannot figure out what's wrong, try to delete the .dat file and try again.
Often you accidentally modify the nedb file (e.g. with autosave of your editor) and you corrupt it.
Recently i started programming with Node JS and found it an amazing replacement for php . In php i used to send get requests with Data in the url .
Something like : http://sample.com/public.php?x=helloworld
How to perform something like this in Node JS or is there a better way to send data to node unlike using the url in the above case .
Also , I have noticed that in some cases like stackoverflow , queries are different and dont include the file name
like /public?= instead of /public.php?=
How is this achieved , i always thought this was something related to REST . Also , if you have the answer you might as well guide me if it could be done with Node and a few sources to learn could be of help too .
the most regular way to use REST api
req.query
// GET /search?q=foo+bar
req.query.q
// => "foo bar"
// GET /phone?order=desc&phone[color]=black&shoe[type]=apple
req.query.order
// => "desc"
req.query.phone.color
// => "black"
req.params
// GET /user/william
req.params.name
// => "william"
req.body(for form data)
// POST /login
req.body.username
// => "william"
req.body.password
// => "xxxxxx"
You'll probably be much better off using a pre-existing module as your web server. You can set one up manually, but you have to know about a lot of potential edge cases and really understand web servers. Most people in node use express. In node, as in any server-side language, you can pass data around in a few ways. The query string is one. You can also put some parameters directly in the url (like "/users/12" where 12 is a user id). Depending on the type of request, you can put data in the body of the request. You can also pass cookies. These are not node-specific. Explaining how express works in a post like this would be crazy, so I'll just give you a short example of a what a route handler matching your example route might look like:
var express = require('express');
var app = express();
app.get('/public', function(req, res, next) {
// Get the value from the query string. Express makes the query
// available as an object on the request parameter.
var x = req.query.x;
// Execute your main logic
doSomethingWithX(x);
// Send a response
res.status(200).json({ foo: 'bar' });
});
I'm making a temporary fake API and am trying to set up a simple request response script in node using express.js to achieve this. It's very strraightforward, A request comes in, is validated and, if valid, is merged with a .json template file and the result returned, thus giving the impression the user was successfully created.
app.post('/agent/user', function(req, res){
var responseTemplate = new jsonRequired('post_user');
var errorTemplate = new jsonRequired('post_user_error');
var payload = req.body;
var responseData;
var hasErrors = false;
console.log('Creating new user');
//Recursive Merge from http://stackoverflow.com/a/383245/284695
responseData = new mergeRecursive(responseTemplate,payload);
if(!payload.username){
hasErrors = true;
errorTemplate.errors.username.push('A username is required.');
}
if (hasErrors){
res.send(errorTemplate,422);
}else{
res.send(responseData,200);
}
});
The problem I'm having is that data is persisting between calls. So if I define a username and name[first] in 1 request and just a username in the 2nd one, both requests come back with the name[first] property.
I have a feeling it's something to do with js closures. Unfortunately, every tutorial I find seems to be about making closures, not avoiding them.
It should work like this:
The client POST's username=user1&name[first]=joe&name[last]=bloggs
The Server loads a json file containing a prepopulated user object: e.g.
{"username":"demo","name":{"first":"John","last":"Doe"}...}
mergeRecursive() merges the payload from the POST request over the template object and returns the new object as the POST response text.
The problem is that with every new request, the server is using the result of step 3 in step 2 instead of reloading the .json file.
That mergeRecursive function has the same caveat as jQuery.extend: it modifies the first object sent into it. In fact, you don't even need to use its return value.
You didn't show the code of jsonRequired function (it's not even clear why you've used new when invoking it), but it looks like this function doesn't create a new object each time it's called, instead fetching this object from some outer repository. Obviously, mergeRecursive modifications for it won't be lost after that function ends.
The solution is using your data object for merging. Like this:
var responseData = {};
...
mergeRecursive(responseData, responseTemplate);
mergeRecursive(responseData, payload);
Merging two objects will make this for you.
If your responseTemplate has parameter, which actual request did not have, then you will end up having it there.
Check definition of word merge ;)
While this doesn't resolve the issue I had, I have found a workaround using the cloneextend package available via npm:
$ npm install cloneextend
This allows me to use the following js:
var ce = require('cloneextend');
...
ce.extend(responseData, responseTemplate);
ce.extend(responseData, payload);