Question: What is async module?
Async is a utility module which provides straight-forward, powerful functions for working with asynchronous JavaScript.
Question: How to install async module?
npm install async
Question: How to include request module in node project?
var async = require('async');
Question: Concatenate the files from different directories?
async.concat(['data', 'data1'], fs.readdir, function(err, files) {
if (err) {
return console.log(err);
}
/*files is now a list of filenames that exist in the 3 directories*/
console.log(files);
});
Question: What are other collection methods available in async ?
concat concatSeries detect detectLimit detectSeries each eachLimit eachOf eachOfLimit eachOfSeries eachSeries every everyLimit everySeries filter filterLimit filterSeries groupBy groupByLimit groupBySeries map mapLimit mapSeries mapValues mapValuesLimit mapValuesSeries reduce reduceRight reject rejectLimit rejectSeries some someLimit someSeries sortBy transform
Question: Give an example of parallel in async?
async.parallel([
function(callback) {
setTimeout(function() {
callback(null, 'one');
}, 200);
},
function(callback) {
setTimeout(function() {
callback(null, 'two');
}, 100);
}
],
// optional callback
function(err, results) {
console.log(results); //['one','two']
});
Question: What other control methods in async?
applyEach applyEachSeries auto autoInject cargo compose doDuring doUntil doWhilst during forever parallel parallelLimit priorityQueue queue race retry retryable seq series times timesLimit timesSeries tryEach until waterfall whilst
Question: Give an example of async.log?
var hello = function(name, callback) {
setTimeout(function() {
callback(null, 'hello ' + name);
}, 1000);
};
async.log(hello, 'World 1'); //Hello World 1
async.log(hello, 'World 2'); //Hello World 2
async.log(hello, 'World 3'); //Hello World 3
Question: What other Utiles methods in async?
Utils apply asyncify constant dir ensureAsync log memoize nextTick reflect reflectAll setImmediate timeout unmemoize
