how to use Mongodb one instance to different-different module in node.js

I'm using mongodb database in node.js with mongodb module. I want to know how to use one mongodb instance into different-different module?

I create a instance of mongodb database inside app.js. And for routing I used another module myroutes.js and I want to re-use the same mongodb instance (which I already created in app.js) inside myroutes.js.

How I do this? I tried it using app.set() but it doesn't work.

You need to visit the singleton design pattern which limits the number of instances of a particular object to just one. This single instance is called the singleton.

Example

var Singleton = (function () {
var instance;

function createInstance() {
    var object = new Object("I am the instance");
    return object;
}

return {
    getInstance: function () {
        if (!instance) {
            instance = createInstance();
        }
        return instance;
    }
};
})();

function run() {

var instance1 = Singleton.getInstance();
var instance2 = Singleton.getInstance();

alert("Same instance? " + (instance1 === instance2));  
}

For MongoDB singleton refer to this https://stackoverflow.com/a/44351125/8201020