Persistent variables in nodeJS

Question

I am writing a node app that needs to remember data across connection iterations of the createServer() callback. Is there a simple way that doesn't involve databases or file r/w? I've sofar attempted creating objects in the respective modules and even main script while passing them into various response handlers, however for every connection they are flushed.

What I mean by that:

require('http').createServer(function(req,res){
        route(req,res,object);
}).listen(cp=80);

object={variable:0}

function route(req,res,object){
    res.end();
    console.log(object.variable);
    object.variable=Math.floor(Math.random()*100);
}

console.log is unsurprisingly throws 0 every connection in this case. Is there any way to create global variables, not in the sense of being available across modules, but persistent unlike var's?

mvbl fst · Accepted Answer · 2012-06-26 01:57:40Z

5

Each module in Node has its own scope, so no, var Foo; does not create a global variable Foo. Use global object from inside the modules.

UPDATE:

require('http').createServer(function(req,res){
        route(req,res,object);
}).listen(cp=8080);

object={variable:0}
global.foo = 'Bar'; // I added this

function route(req,res,object){
    res.end();
    console.log(object.variable);
    console.log("foo = %s", global.foo); // I added this too
    object.variable=Math.floor(Math.random()*100);
}

And it logs "foo = Bar" as expected as well.

edited Jun 26, 2012 at 1:57

answered Jun 26, 2012 at 0:01

mvbl fst

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3 Comments

mvbl fst Over a year ago

How did you test? I just ran your code in Node and it works as expected.

TERMtm Over a year ago

As it turns out, I infact had a programming fluke where I created objects (sessions) and included a self destruct timeout in them. Apparently what happened is that, for the timers' value, I was inputting a math equation that apparently failed to parse. As a result, the variables would self destruct in under 318 milliseconds. Fun stuff. Also worth noting, you don't need to use the global namespace for this to work; neither do you need to declare the variable inside of main module if you just so happen to have the callback in a require. An update would be greatly appreciated, thanks again!

mvbl fst Over a year ago

In this specific case no, you don't need a global. If you load modules async with require() than you do need as what you declared here (say, app.js) will not be visible in the modules. There you need to use a global object.

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