I'm trying to pass objects from one client to another client, e.g. pieces in a multiplayer board game. I have a working solution using JSON.parser and __proto__, but I'm curious to know if there is a better way.
Client sends:
var my_piece = new BoardPiece();
// ... my_piece is assigned data, like x-y coordinates
socket.send(JSON.stringify(my_piece));
Server forwards the piece to others:
client.broadcast(piece);
Another client receives:
var your_piece = JSON.parse(json);
your_piece.__proto__ = BoardPiece.prototype; // provide access to BoardPiece's functions
It's the last step where I use __proto__ that I'm concerned I may be shooting myself in the foot. Is there a better suggestion?
// clientone.js
var piece = new BoardPiece();
// ...
socket.send(JSON.stringify(piece));
// clienttwo.js
var piece = BoardPiece.Create(JSON.parse(json));
...
// BoardPiece.js
function BoardPiece() {
}
BoardPiece.prototype.toJSON = function() {
var data = {};
data.foo = this.foo;
...
return data;
};
BoardPiece.Create = function(data) {
var piece = new BoardPiece();
piece.foo = data.foo;
...
return piece;
}
Firstly using the toJSON method on your objects allows JSON.stringify to immediatly convert your object to JSON. This is part of the JSON API. The JSON API will call the toJSON method if it exists and converts that object to JSON.
This basically allows you to serialize your object as and how you want.
The second part is adding a factory method as a property of your constructor which takes your serialized JSON data and creates a new boardpiece. It will then inject your serialized data into that boardpiece object.
So your serializing only the data you care about and then passing that data through a factory method. This is the best way to send custom objects from one client to another.
There are a bunch of object syncing projects for node that might make life easier. For starters, check out:
NowJS
node-object-sync
Re-using Backbone.js Models on the server with Node.js and Socket.io to build real-time apps
Have tou tried jQuery's $.extend() method? http://api.jquery.com/jQuery.extend/
Related
I'm trying to create a save/load function for my game in js, but I have basically no idea with how to go through with doing this. I can save variables to a JSON file or LocalStorage, but I don't know how to load them back into the program. I'm also pretty sure I'm exporting variables the wrong way as well. Any help?
Normally, I use JSON format to store and read data (of any type).
To save data (using key gamedata as example):
var myData = {
name: 'David',
score: 10
}
localStorage.setItem('gamedata', JSON.stringify(myData));
** without JSON.stringify, you data will be saved as string [Object object]
To retrieve the data back:
var savedData = localStorage.getItem('gamedata'); // savedData is string
var myData = JSON.parse(savedData); // parse JSON string to java object
setup a bin on www.myJSON.com. p5 has built in functionality for ajax requests such as loadJSON. that way it's not in local storage and you can access your data if you have it on github. I know your struggle, I used to deal with this sort of issue myself before I found myJSON
I'm relatively new to Javascript and Node and I like to learn by doing, but my lack of awareness of Javascript design patterns makes me wary of trying to reinvent the wheel, I'd like to know from the community if what I want to do is already present in some form or another, I'm not looking for specific code for the example below, just a nudge in the right direction and what I should be searching for.
I basically want to create my own private IFTTT/Zapier for plugging data from one API to another.
I'm using the node module request to GET data from one API and then POST to another.
request supports streaming to do neat things like this:
request.get('http://example.com/api')
.pipe(request.put('http://example.com/api2'));
In between those two requests, I'd like to pipe the JSON through a transform, cherry picking the key/value pairs that I need and changing the keys to what the destination API is expecting.
request.get('http://example.com/api')
.pipe(apiToApi2Map)
.pipe(request.put('http://example.com/api2'));
Here's a JSON sample from the source API: http://pastebin.com/iKYTJCYk
And this is what I'd like to send forward: http://pastebin.com/133RhSJT
The transformed JSON in this case takes the keys from the value of each objects "attribute" key and the value from each objects "value" key.
So my questions:
Is there a framework, library or module that will make the transform step easier?
Is streaming the way I should be approaching this? It seems like an elegant way to do it, as I've created some Javascript wrapper functions with request to easily access API methods, I just need to figure out the middle step.
Would it be possible to create "templates" or "maps" for these transforms? Say I want to change the source or destination API, it would be nice to create a new file that maps the source to destination key/values required.
Hope the community can help and I'm open to any and all suggestions! :)
This is an Open Source project I'm working on, so if anyone would like to get involved, just get in touch.
Yes you're definitely on the right track. There are two stream libs I would point you towards, through which makes it easier to define your own streams, and JSONStream which helps to convert a binary stream (like what you get from request.get) into a stream of parsed JSON documents. Here's an example using both of those to get you started:
var through = require('through');
var request = require('request');
var JSONStream = require('JSONStream');
var _ = require('underscore');
// Our function(doc) here will get called to handle each
// incoming document int he attributes array of the JSON stream
var transformer = through(function(doc) {
var steps = _.findWhere(doc.items, {
label: "Steps"
});
var activeMinutes = _.findWhere(doc.items, {
label: "Active minutes"
});
var stepsGoal = _.findWhere(doc.items, {
label: "Steps goal"
});
// Push the transformed document into the outgoing stream
this.queue({
steps: steps.value,
activeMinutes: activeMinutes.value,
stepsGoal: stepsGoal.value
});
});
request
.get('http://example.com/api')
// The attributes.* here will split the JSON stream into chunks
// where each chunk is an element of the array
.pipe(JSONStream.parse('attributes.*'))
.pipe(transformer)
.pipe(request.put('http://example.com/api2'));
As Andrew pointed out there's through or event-stream, however I made something even easier to use, scramjet. It works the same way as through, but it's API is nearly identical to Arrays, so you can use map and filter methods easily.
The code for your example would be:
DataStream
.pipeline(
request.get('http://example.com/api'),
JSONStream.parse('attributes.items.*')
)
.filter((item) => item.attibute) // filter out ones without attribute
.reduce((acc, item) => {
acc[item.attribute] = item.value;
return acc;
.then((result) => request.put('http://example.com/api2', result))
;
I guess this is a little easier to use - however in this example you do accumulate the data into an object - so if the JSON's are actually much longer than this, you may want to turn it back into a JSONStream again.
I want to pass a LatlngBounds object from a client to nodejs server.
var bounds = map.getBounds();
socket.emit('sendbounds', bounds);
In the server:
socket.on('sendbounds',function(data){
console.log(data);
data.getNorthEast();// undefined method getNorthEast()
}
The server can get the data sent from the client. However I am unable to use method getNorthEast().
My solution is to create an object LatlngBounds:
bounds = new google.maps.LatLng(data.Ea.k, data.va.j),
new google.maps.LatLng(data.Ea.j, data.va.k));
However this is not recommended because we cannot sure the key names are always 'Ea' and 'va'.
I notice that sometimes the key names are "Fa" and wa". They are "undocumented properties". They change with API releases.
Any solution to solve this problem?
I tried it that way, too, but had the same problem: Can't rely on the variable names.
Instead, I passed it to the server as a string instead of an object:
corners = map.getBounds();
var c = corners.toString();`
Then use whatever AJAX library to send the string to the server.
It looks something like this:
((33.94310833405608, -118.44952616442868), (33.985820303992334, -118.34120783557125))
You will have to pick it apart using a regexp, but at least it's reliably formatted.
I’m trying to understand how and where to use data after a fetch using Backbone.js but I’m a little confused.
I’ll explain the situation.
I have an app that, on the startup, get some data from a server. Three different kind of data.
Let’s suppose Airplanes, Bikes, Cars.
To do that, I’ve inserted inside the three collections (Airplanes, Cars, Bikes) the url where to get these data.
I’ve overwrited the parse method, so I can modify the string that I get, order it, and put it in an object and inside localstorage. I need it to be persistent because I need to use those 3 data structure.
So with a fetch i get all those data and put them inside localstorage. Is it correct doing it that way?
Now i need to make other calls to the server, like “get the nearest car”.
In the view i need to see the color, name and model of the car, all that informations are inside the object “Cars” in localstorage.
In my view “showcars.view” I just call a non-backbone js, (not a collection, model or view) where i get all the informations i need. In this js i do:
var carmodel = new Car(); //car is the backbone model of the cars
carmodel.url = '/get/nearest/car'; //that give id of the nearest car
carmodel.fetch ({
success: function () {}
//here i search the Cars object for a car with the same id
//and get name, color, model and put them in sessionstorage
})
So after that call, in the view I can get the data I need from the sessionstorage.
Is that a bad way of doing things? If so, how i should fetch and analyze those informations? I should do all the calls and operations inside the models?
Thanks
This would be the way that you might implement what you want.
var Car = Backbone.Model.extend();
var Cars = Backbone.Collection.extend({
model: Car,
url: '.../cars'
});
var NearestCar = Backbone.Model.extend({
url: '...nearest/car'
});
var cars = new Cars();
var nearestCar = new NeaerestCar();
cars.fetch({
success: function() {
nearestCar.fetch({
success: function(model) {
var oneYouWant = cars.get(model.get('id'));
// do something with your car
// e.g.:
// var carView = new CarView({model: oneYouWant});
// $('body').append(carView.render().el);
});
});
});
});
In general, Backbone keeps everything in memory (that is, the browser memory) so there is no need to save everything to local storage, as long as your Collection object is somehow reachable from the scope you are sitting in (to keep things simple let's say this is the global window scope).
So in your case I will have something like three collections:
window.Cars
window.Airplanes
window.Bikes
Now you want the nearest. Assuming you are in a Backbone View and are responding to an event, in your place I would do something like this (just shows the meaningful code):
var GeneralView = Backbone.View.extend({
events: { "click .getNearestCar": "_getNearestCar" },
_getNearestCar: function () {
$.getJson('/get/nearest/car', function (data) {
// suppose the data.id is the id of the nearest car
var nearestCar = window.Cars.get(data.id)
// do what you plase with nearestCar...
});
}
});
So thanks to SO I can pass an object from node to the client, but then getting it into a knockout view model is a bit awkward. These are the steps I have so far (I've included links to the relevant lines as they appear in my github project. Thought the context might help.):
Apply JSON.stringify and pass to the jade file
recipeJSON: JSON.stringify(recipe);
Wrap this in a function in a header script that just parses the JSON and returns the result
script
function getRecipeObject() {
var r = '!{recipeJSON}';
return JSON.parse(r);
}
Call this function and pass the result to a view model constructor
self.recipe = ko.observable(new Recipe(getRecipeObject()));
This works but is there a better way?
Question clarification (Edit): I feel step 2 shouldn't be necessary. Is there a way to directly pass the JSON from node to the Recipe() constructor, without the getRecipeObject() acting as an intermediate step? I tried passing recipeJSON in directly like so
self.recipe = ko.observable(JSON.parse('!{recipeJSON}'));
That doesn't work I think because its not a jade template and has no access to the variable.
According to the answer to this question rendering data into scripts is bad practice and I should instead make an XHR call on page load instead.
Edit
I just saw you linked a github repo! So you're already familiar with most of this...you even have an endpoint set up at /recipe/:id/view, so now I'm really confused...what isn't working out for you? Just the last step of deserialization using ko.utils.*?
Sorry about all the exposition -- I thought this was way more rudimentary than it actually was; I hope no offense taken there!
You really don't want to return a script to execute -- instead, treat this as a DTO: an object that just stores data (no behaviors). An example would be:
{
recipeID: 12,
reviewIDs: [42, 12, 55, 31],
rating: 4.2
recipeName: "A super tasty pie!"
}
This object (representation) is a projection -- a simplified version of the full data stored in the database.
The next step is to create an endpoint to access that data on the server. Let's assume you're using Express:
var app = express();
app.get('/recipes/:recipeID', function(req, res) {
var recipeID = req.params.recipeID;
// It would be cool if this existed, huh?
getRecipeAsync(recipeID, function(recipe) {
res.status(200).json(recipe);
});
});
If you send a GET request to your (hypothetical) application (let's say it's https://localhost:8080/recipes/12), you'll get json representing the (admittedly imaginary) recipe with ID 12.
You can accomplish getting the JSON with jQuery (or any other library that makes XHR nice and pretty)
var recipeID = 12;
$.ajax({
url: "/recipes/" + recipeID,
type: "GET"
}).then(function(recipe) {
console.log("Hey! I got the recipe: %O", recipe);
// Note: you might need to use ko.utils.fromJS(recipe) if the returned
// data is JSON that ISN'T deserialized into an object
var recipeObservable = ko.utils.fromJS(recipe);
});
That's about everything you need to know. Obviously, the devil's in the details, but that's basic idea; let me know if that helps!