Nodejs send waterfall requests - node.js

Question

I have dynamic array with foldername and creating a zip using zipFolder
I am facing issues as the library is async i.e
zipFolder(source,dest,callback)
Because its a async call it take times and I want to block the next request unless the first one reponse is true,
function (req, res)
var folder = ['N','PP','Y'];//dynamic just an example
for( var i = 0 ; i < folder.length ; i++) {
var source = path.join(basePath,'/download/'+folder[i]);
var dest = path.join(basePath,'/createZip/'+folder[i]+'.zip');
console.log('sending',folders[i])
//this is async
zipFolder(source,dest, function(err) {
if(err) {
console.log('oh no!', err);
} else {
console.log('EXCELLENT');//want to send the second,third,fourth if success
}
});
}
Summary:
output should be like this:
sending file 1 if success/response sending file 2 if success/response
want something like waterfall wait for callback reponse to send the second file
plus I want a method to know the done call back so I can send back the reponse

Answer 1

you can use each as like:
var each = require('async-each-series')
var folder = ['N','PP','Y'];
each(folder, function(items,callback){
//insert each items to db in async way
var source = path.join(basePath,'/download/'+items);
var dest = path.join(basePath,'/createZip/'+items+'.zip');
zipFolder(source,dest, function(err) {
if(err) {
console.log('oh no!', err);
} else {
console.log(items,'inserted')
callback()
}
});
},function(err){
if(err) console.log('error occured')
console.log('all items uploaded');
});

Answer 2

Try with async waterfall method
https://caolan.github.io/async/docs.html#waterfall
Runs the tasks array of functions in series, each passing their
results to the next in the array. However, if any of the tasks pass an
error to their own callback, the next function is not executed, and
the main callback is immediately called with the error
async.waterfall([
function(callback) {
callback(null, 'one', 'two');
},
function(arg1, arg2, callback) {
// arg1 now equals 'one' and arg2 now equals 'two'
callback(null, 'three');
},
function(arg1, callback) {
// arg1 now equals 'three'
callback(null, 'done');
}
], function (err, result) {
// result now equals 'done'
});
UPDATE
in your usecase eachSeries is more applicable.
var folder = ['N','PP','Y'];
async.eachSeries(folder, function(item,callback){
var source = path.join(basePath,'/download/'+item);
var dest = path.join(basePath,'/createZip/'+item+'.zip');
zipFolder(source,dest, function(err) {
if(err) {
console.log('oh no!', err);
callback();
} else {
console.log('EXCELLENT');//want to send the second,third,fourth if success
callback();
}
});
},function(){
console.log('all items uploaded');
}); .