I'm new to Node.js, so I'm still wrapping my head around asynchronous functions and callbacks. My struggle now is how to return a response after reading data from a file in an asynchronous operation.
My understanding is that sending a response works like this (and this works for me):
app.get('/search', function (req, res) {
res.send(request received);
});
However, now I want to read a file, perform some operations on the data, and then return the results in a response. If the operations I wanted to perform on the data were simple, I could do something like this -- perform them inline, and maintain access to the res object because it's still within scope.
app.get('/search', function (req, res) {
fs.readFile(data.txt, function(err, data) {
result = process(data.toString());
res.send(result);
});
});
However, the file operations I need to perform are long and complicated enough that I've separated them out into their own function in a separate file. As a result, my code looks more like this:
app.get('/search', function (req, res) {
searcher.do_search(res.query);
// ??? Now what ???
});
I need to call res.send in order to send the result. However, I can't call it directly in the function above, because do_search completes asynchronously. And I can't call it in the callback to do_search because the res object isn't in scope there.
Can somebody help me understand the proper way to handle this in Node.js?
