How to return something async with require?

Question

How to return something async with require?

I'm a little new to this so bear with me...

app.js:

var testVariable = require('./test');
console.log(testVariable);

test.js:

setTimeout(function() {
    exports.something = "HELLO!";
}, 10000);

In this scenario, the output is {}. If exports.something = "HELLO!"; is moved outside the setTimeout, the output is { something: 'HELLO' }.

I'm trying to connect to a DB and it's taking a second as you can imagine. How can I return something that takes a little while to process to app.js?

node.js
return

Answer 1

You can't.

require is synchronous, node initially had asynchronous require but it was dropped because people ended up abusing it, and it was not well maintained.

I suggest you do something like

exports.something = promise;

And return a promise for the value, or a callback handler.

The simplest implementation could be

var callback=function(){},fired=false,data;
exports.handle = function(cb){
    callback = cb;
    if(fired === true){ //already fired once
      cb(data);//fire again
    }
});

setTimeout(function() {
    cb("HELLO!");
    fired = true;
    data = "HELLO!";
}, 10000);

Then you could use

require("myModule").handle(function(data){
   //work with data
});

The idea is that instead of returning the value, you're returning a function to execute when the value is ready on the value. (Also, I've included some boilerplate so that it executes if the callback finished before the handler was assigned)