How to write thread safe code in node.js

Here's a part of my app.js:

var connections = [];

function removeConnection(res) {
    var i = connections.indexOf(res);
    if (i !== -1) {
        connections.splice(i, 1);
    }
}

And I call removeConnection when a request is closed:

req.on('close', function () {
    console.log("connection closed");
    removeConnection(res);
});

I wonder if the above code is thread safe? I mean as Node.js is event driven, is the followinf scenario possible?

1. connections is [a,b,c]
2. threadB calls removeConnection
3. in threadB.removeConnection: i = 1
4. threadA calls removeConnection
5. in threadA.removeConnection: i = 0
6. in threadA.removeConnection: connections.splice(0, 1); => connections is [b,c]
7. in threadA.removeConnection: connections.splice(1, 1); => connections is [b]

As you see in this scenario, threadC's connection would be removed instead of threadB's.

Can this happen? If yes, then how should I fix the code?