CODEWITHSUNDEEP
javascriptnode.jsconstructor
Webster
Webster

Reputation: 1153

Javascript / Node Js - Create New variable for each instance

I'm creating a game bot on telegram using node js.

Currently I'm facing a problem on shared variable (module.exports). I'm storing some of the data on the variable. And the problem is, the shared variable index always change. For example, please refer to my code below

var sharedVar = [];

createNewRoom = function(res) { 

 var index = sharedVar.length;

 sharedVar.push({ groupId : res.chat.id }); // every time this function is invoked, it will create a new array inside sharedVar object

//Here comes the problem, it's about the index, 
//because I'm using sharedVar to store arrays, then it will become a problem, 
//if one array is deleted (the index will change)

 var groupId = sharedVar[index].groupId; // it runs OK, if the structure of array doesn't change, but the structure of array change, the index will be a wrong number

        }

As you can see, i got callGameData function, when i call it, it will show the last value of sharedVar, it's supposed to show the current room values / data.

As i mention on the code above, it's all about the dynamic array in the sharedVar object, the index will change dynamically

Any thoughts to tackle this kind of issue? I was thinking about using a new sharedVar object everytime the createNewRoom function is invoked, but the thing is, i have to use sharedVar in many different function, and i still can't figure it out on using that method.

EDIT

This is the second method

var gameData = undefined;

createNewRoom = function() {
 this.gameData = new myConstructor([]); // it will instantiate a new object for each new room

}

myConstructor = function(data) {
 var _data = data;
 this.object = function() {
  return _data;
 }
}

callGameData = function() {
 console.log(gameData);
}

Upvotes: 1

Views: 1388

Answers (2)

PMV
PMV

Reputation: 2128

An array is fundamentally the wrong data type to use if you want to keep indices the same even in the face of removing entries.

A better method is to use properties of an object. For example:

var roomCache = { nextId: 1 };

createNewRoom = function(res) { 
    roomCache[roomCache.nextId++] = {groupId: res.chat.id}; // Add a new object to the cache and increment the next ID
}

After adding two elements, you'll have the rooms in roomCache[1] and roomCache[2] - if you want to start at zero just change the original value of nextId. You can delete elements in this object and it won't shift any keys for any other objects - just use delete roomCache[1] for example to get rid of that entry.

This assumes there isn't a better ID out there to use for the cache - if, for example, it made more sense to lookup by res.chat.id you could certainly use that as the key into roomCache rather than an auto-incrementing number. Here's how it would look like to cache the values by the group ID instead:

var roomCache = { };

createNewRoom = function(res) { 
    roomCache[res.chat.id] = {groupId: res.chat.id}; // Assumes res.chat.id is not a duplicate of an already cached obhect
}

Now you could just look up by group ID in the cache.

Upvotes: 1

Juan L
Juan L

Reputation: 1731

Yes, it's definitely a problem cause you are not keeping track of the index in a logical way, you are relying on position on the array which it changes, you need something that doesn't change over time to keep consistency and supports deletition of the element without affecting the rest of the elements. You could use mongo to store the generated rooms by id or maybe redis or some kind of key value pair database to store that kind of information.

Upvotes: 1

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