How to Wait in Node.js

Question

Here is a question about what I would think would be a simple pattern in node js.

Here is my example in coffeescript:

db_is_open = false

db.open ->
  db_is_open = true

wait = ->
wait() until db_is_open

And here again in javascript:

var db_is_open = false;

db.open(function() {
  db_is_open = true;
});

function wait() {};
while (not db_is_open) { wait()};

This does not work at all because the while loop never relinquishes control, which I guess makes sense. However how can I tell the wait function to try the next callback in the queue?

Answer 1

I like to use the async module when I have bits of code that need to run synchronously.

var async = require('async');

async.series([
  function(next){
    db.open(next)
  }
, function(next){
    db.loadSite('siteName', next)
  }
], function(err){
  if(err) console.log(err)
  else {
    // Waits for defined functions to finish
    console.log('Database connected')
  }
})

Answer 2

Why are you waiting, and not just using a callback that runs inside of the function passed to db.open? This is pretty much idiomatic Node code:

db.open(function() {
  // db is now open, let's run some more code
  execute_db_query();
});

Basically, you should simply follow the patterns laid out in the documentation.