Why is async.map passing only the value of my JSON? - json

Question

I have a function in node.js that looks like this:
exports.getAllFlights = function(getRequest) {
// this is the package from npm called "async"
async.map(clients, getFlight, function(err, results) {
getRequest(results);
});
}
The variable clients should be a JSON that looks like this:
{'"A4Q"': 'JZA8187', "'B7P"': 'DAL2098' }.
I expect that the map function will pass the individual indices of the array of the variable clients to getFlight. However, instead it passed the values of that each(ex: 'DAL2098', 'JZA8187' and so on).
Is this the expected functionality? Is there a function in async that will do what I want?
The signature of getFlight is getFlight(identifier, callback). Identifier is what is currently messed up. It returns callback(null, rtn). Null reprsents the nonexistence of an error, rtn represents the JSON that my function produces.

Answer 1

Yes, that's the expected result. The documentation is not very clear but all iterating functions of async.js pass the values of the iterable, not the keys. There is the eachOf series of functions that pass both key and value. For example:
async.eachOf(clients, function (value, key, callback) {
// process each client here
});
Unfortunately there is no mapOf.
If you don't mind not doing things in parallel you can use eachOfSeries:
var results = [];
async.eachOfSeries(clients, function (value, key, callback) {
// do what getFlight needs to do and append to results array
}, function(err) {
getRequest(results);
});
Another (IMHO better) workaround is to use proper arrays:
var clients = [{'A4Q': 'JZA8187'},{'B7P': 'DAL2098'}];
Then use your original logic. However, I'd prefer to use a structure like the following:
var clients = [
{key: 'A4Q', val: 'JZA8187'},
{key: 'B7P', val: 'DAL2098'}
];

Answer 2

First create a custom event. Attach a listener for return data. then process it.
var EventEmitter = require('events');
var myEmitter = new EventEmitter();
myEmitter.emit('clients_data',{'"A4Q"': 'JZA8187'}); //emit your event where ever
myEmitter.on('clients_data', (obj) => {
if (typeof obj !=='undefined') {
if (obj.contructor === Object && Object.keys(obj).lenth == 0) {
console.log('empty');
} else {
for(var key in obj) {
var value = obj[key];
//do what you want here
}
}
}
});

Answer 3

Well, you need to format your clients object properly before you can use it with async.map(). Lodash _.map() can help you:
var client_list = _.map(clients, function(value, key) {
var item = {};
item[key] = value;
return item;
});
After that, you will have an array like:
[ { A4Q: 'JZA8187' }, { B7P: 'DAL2098' } ]
Then, you can use async.map():
exports.getAllFlights = function(getRequest) {
async.map(client_list, getFlight, function(err, results) {
getRequest(results);
});
};