A strange feature of node.js

Noticed a strange feature of node.js.

For example:

Let's say, I've got some variable on node.js server: var user_id = '1';, in which the stored user id which is connected to the server.

user1 have var user = 1;

user2 have var user = 2;

...

user99 have var user = 99;

But if at some point I will demand from the server variable user - I will return the id of the last user who rewrote her.

Is that right? So it should be? I thought, node.js for each user creates a flow/process ...

Thanks for your answer!

index.js

dNode({
    connect: function(data, callback) {
        IM.iUserId = data.user_id;
        IM.start();
    }
});

im.js

var IM = {
    iUserId: false,
    start: function() {
        console.log(this.iUserId);
    }
};