This is the initial code that works fine:
var fs = require('fs');
var async = require('async');
var addErrParm = function (err, done) {return function(exists) {
done(err, exists);
}}
function testAsync() {var response = '';
function checkIfTheFileExists(done) {
fs.exists('file.txt', addErrParm(null, done));
}
function readTheFile(exists, done) {
if (!exists) {
done('notFound');
} else {
fs.readFile('file.txt', 'utf8', done);
}
}
function showTheFile(err) {
if (err) {
response = err;
} else {
response = 'file was read';
}
console.log(response);
}
async.waterfall([ // <-- waterfall
checkIfTheFileExists,
readTheFile
], showTheFile);
}
testAsync() // "file was read"
The following doesn't seem to work. Only difference is the first uses async.parallel instead of async.series.
var fs = require('fs');
var async = require('async');
var addErrParm = function (err, done) {return function(exists) {
done(err, exists);
}}
function testAsync() {var response = '';
function checkIfTheFileExists(done) {
fs.exists('file.txt', addErrParm(null, done));
}
function readTheFile(exists, done) {
if (!exists) {
done('notFound');
} else {
fs.readFile('file.txt', 'utf8', done);
}
}
function showTheFile(err) {
if (err) {
response = err;
} else {
response = 'file was read';
}
console.log(response);
}
async.series([ // <-- only line of code that differs.
checkIfTheFileExists,
readTheFile
], showTheFile);
}
testAsync() // <-- no output is displayed on the console, not even a blank line.
The async.series version did not produce any output on the console. What could be causing this issue?
I also attempted an async.parallelLimit version with the limit set to 1. I expected it to execute the tasks in series due to the limit but again did not see any output on the console. Here is the async.parallelLimit version:
var fs = require('fs');
var async = require('async');
var addErrParm = function (err, done) {return function(exists) {
done(err, exists);
}}
function testAsync() {var response = '';
function checkIfTheFileExists(done) {
fs.exists('file.txt', addErrParm(null, done));
}
function readTheFile(exists, done) {
if (!exists) {
done('notFound');
} else {
fs.readFile('file.txt', 'utf8', done);
}
}
function showTheFile(err) {
if (err) {
response = err;
} else {
response = 'file was read';
}
console.log(response);
}
async.parallelLimit([ // <--- this line is different
checkIfTheFileExists,
readTheFile
], 1, showTheFile); // <--- and this line is different. I added the "1".
}
testAsync() // <--- no output on the console.
The file does exist in all three test cases.