Handle timeout callback event in readFile method of Node.js - node.js

Question

My requirement is like below:
I have 3 Big files big_file_1, big_file_2 and big_file_3. I want to read this 3 big files asynchronously and process my rest of the code only after the reading of all files are completed.
fs.readFile('big_file_1', function (err, data) {
if (err) throw err;
content_1 = data;
});
fs.readFile('big_file_2', function (err, data) {
if (err) throw err;
content_2 = data;
});
fs.readFile('big_file_3', function (err, data) {
if (err) throw err;
content_3 = data;
});
// Do something with content_1, content_2 and content_3
How can I achieve this in Node.JS ?

Answer 1

You can do it using the parallel function of the async library:
async.parallel([
fs.readFile.bind(fs, 'big_file_1'),
fs.readFile.bind(fs, 'big_file_2'),
fs.readFile.bind(fs, 'big_file_3')
], function (err, results) {
if (err) throw err;
content_1 = results[0]
content_2 = results[1]
content_3 = results[2]
/* TODO do some cool stuff */
})
Alternatively, you can do it manually:
int steps_done = 0
fs.readFile('big_file_1', function(err, data) {
if (err) throw err
content_1 = data
if (++steps_done == 3) do_next_step()
})
fs.readFile('big_file_2', function(err, data) {
if (err) throw err
content_2 = data
if (++steps_done == 3) do_next_step()
})
fs.readFile('big_file_3', function(err, data) {
if (err) throw err
content_3 = data
if (++steps_done == 3) do_next_step()
})