javascript - node js - understanding variable scopes

Question

I am fairly new to node.js and trying to get my head around the asynchronous processing loop etc.

So let's assume I have an array var counter = [];defined at the top of my server.js file

Then I have a POST handler as follows

app.post("/test_post", function(req, res) {
    console.log(req.body);
    counter ++;
})

I am trying to understand the scope of the counter variable - Will it be different for every client or will it be common across clients.

Also, I am looking for a way to increment counter for the same client, so in other words, I'd like a counter for each visiting client.

How can I achieve this? Thanks

Answer 1

I am trying to understand the scope of the counter variable - Will it be different for every client or will it be common across clients.

It will be common across clients since you are defining it globally.

Also, I am looking for a way to increment counter for the same client, so in other words, I'd like a counter for each visiting client.

Basically what you need to do is to listen on connection & disconnection of every client and save the counter in the respective client object.

Have a look at this implementation it may help you.