5

I have a global variable which looks like this:

var socket_x = 'whatever';

The thing is that "x" would depend on the user session. Let's say the user id is 123, i want the global variable to be:

var socket_123 = 'whatever';

This way, each user browsing will have his own socket set as global variable.

I just don't know how to do this.

I know I can use: 

eval('socket_' + userId)   = 'whatever'; //not recommended
window['socket_' + userId] = 'whatever'; //best

but if I want to declare the global variable like this, it won't work:

var eval('socket_' + userId) = 'whatever';

Can someone help me on this one?

Thank you.

PS: I know "eval" should not be used for this but it's just for the illustration sake.

EDIT:

Thank you for your answer, all of you, but it just doesn't work.

This is what I have so far for my global variable (it works as it is but I don't want to mix php with javascript):

var socket_<?php echo $_SESSION['user_id'];?> = io.connect( 'http://pubsub.pubnub.com', pubnub_setup_private );

if I do this instead, like you suggest:

window['socket_'+actual_user_id]= io.connect( 'http://pubsub.pubnub.com', pubnub_setup_private );

it just won't work.

if I do this as a local variable, it works:

eval('socket_'+actual_user_id).emit( 'all', msg_all );

But if I do that, it doesn't:

window['socket_'+actual_user_id].emit( 'all', msg_all );

So I got 2 problems here:

  • window never works for me, eval does.
  • eval works as a local variable but not as a global one. It seems that "var" is needed but using "var" just before eval is not accepted.

I'm ok with avoiding eval but I just don't know how.

PS: I'm on a global context here.

Baylock
  • 1,246
  • 4
  • 25
  • 49
  • Is this code running in a browser? And you can include `var` in the `eval` *not that I'd recommend it*. `eval('var socket_' + userId + ' = "whatever"');` – cliffs of insanity May 14 '12 at 17:15
  • Why are you using a `==` comparison in you second code block in your edit? Did you mean to use assignment? – apsillers May 14 '12 at 17:16
  • 1
    Also, it really sounds like you should be using an Object. `var sockets = {};` Then each user's socket is added: `socket['socket_' + userId] = "whatever";` – cliffs of insanity May 14 '12 at 17:17
  • The "==" is a typo here, not in my script (I corrected it on my question). For the object thing, I'm using "PubNub" and this is the syntax they recommend to make the calls to their library. I tried t your way but it is not accepted. – Baylock May 14 '12 at 17:20
  • Can you confirm that `eval("socket_"+actual_user_id) !== window["socket_"+actual_user_id]`? If so, you have scoping issues causing the variable name in `eval` to refer to a non-global variable. – apsillers May 14 '12 at 17:21
  • I confirm that, for a local variable (inside a function) eval works but not Window which would make sense. But If I'm on a global level, none of them would work. It seems that I need to declare them as "var" and if i do so, none of them is accepted. Thank you for your help. – Baylock May 14 '12 at 17:23
  • Yes, in a browser. I'm just calling the pubnub service via my client side script. The NodeJS is on their side. – Baylock May 14 '12 at 17:37

2 Answers2

5
window['socket_'+userId] = "whatever";

That should work just fine. Do NOT use eval for something as trivial as this.

Although, even better would be an array:

socket[userId] = "whatever";
Niet the Dark Absol
  • 320,036
  • 81
  • 464
  • 592
  • thank you. Please read my first question as I edited it to be more accurate. – Baylock May 14 '12 at 17:02
  • 1
    Hmm... is there ever going to be more than one user on the same *browser window*? If not, why not just call the variable `session` and forget about having the user ID on it? – Niet the Dark Absol May 14 '12 at 17:03
  • No. One user only. But I just don't get what you are refering to as the variable session. The user id variable is the variable session I got via ajax. As you can see, using the php variable works just fine, I just prefer to use a javascript variable in order to avoid to mix php and javascript on the same script. – Baylock May 14 '12 at 17:05
  • To complete my answer: My script works as it is but the reason I want to get rid of the php variable inside the script is that it is the only thing that prevents me from calling my file 'javascript.js' instead of 'javascript.php'. Not a big deal but it would be sad to let it as it is just because I couldn't find a way to declare a variable correctly. – Baylock May 14 '12 at 17:56
  • Personally I like to include a small script at the top of my page with things like `USERNAME="=$username?>"` and so on, then have external scripts refer to those global variables. – Niet the Dark Absol May 14 '12 at 18:18
  • Thank you. It would make sense if I had plenty of those. I just think that including an external file having one single variable set is not ideal. Not mentioning that it is not the issue as I still don't know how to create a new variable from that variable I'm getting from the external script. The issue remains the same. – Baylock May 14 '12 at 18:25
  • I didn't mean a new file, I meant a ` – Niet the Dark Absol May 14 '12 at 19:26
1

A variable attached to window is a global variable. For example:

var myVar = 'hello';
alert( window.myVar );

... will alert 'hello' (assuming this code is run in the global context, of course).

EDIT: I would try ensuring your variable is being attached to the window object by specifying it manually with window[xxx] = yyy instead of var xxx = yyy. This means it will always work even if it's in a function call. Try playing with this fiddle and see if you can break it the same way as your real code: http://jsfiddle.net/2hYfa/

kitti
  • 14,663
  • 31
  • 49
  • thank you. Please read my first question as I edited it to be more accurate. – Baylock May 14 '12 at 17:02
  • I'm ok with what you say but as you can see on my edited question, it just doesn't work for me. – Baylock May 14 '12 at 17:17
  • Ok, I tried and this is what I get => if I try to display it on a div, like you did on jsfiddle; nothing is displayed. If I try with a console.log or alert function, I get this: [object object]. Thank you for your help. – Baylock May 14 '12 at 17:36
  • That seems to be working then. My example used a string for simplicity, but you are using an object. If the alert is showing object Object then it's probably the right object. – kitti May 14 '12 at 17:44
  • Probably. But it seem that this variable should be declared as "var". I read very thoroughly what you said before about window and global variables and I get it. But it still doesn't want to work. My edited question shows that I did what you suggested but my chat (this is what it's about) is frozen since then. – Baylock May 14 '12 at 17:49