How to work with the async module?

Question

How to work with the async module?

There is a module that makes a request to the database. Call it from another place but due to asynchrony, he has no time to work out. How to call it synchronously?

createExtraData function() {
 var regionList = regionsLists.getRegionsList();
 console.log(regionList) //Here is undefined, the query to the database in the module have not yet met
sendData()
}

It is possible a code sample how to fix? I read about promises but do not understand how to use them here.

Maynard_Schiller asked July 9th 19 at 10:22

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More answers about "How to work with the async module?"

3 answers

orrin_Hilpert answered on July 9th 19 at 10:28

You nogino that come to mind:

var regionList = regionsLists.getRegionsList().then(function(data) { console.log(data) })

How to do it: https://learn.javascript.ru/promise

Sarai.Rutherford53 answered on · Accepted Answer · 2019-07-09T10:24:01.007Z

All through as and!
In the settings getRegionsList transfer callback, in which you'll perform actions with the received data.
Asynchronous functions usually do not return (via return). Their task is to invoke the callback and pass it the result of function execution (in your case the query to the database).

UPD: example (your module)

//...

module.exports.getRegionsList = function(callback)
{
 /*abstract an example of a DB query*/
db.req(callback);
/* 
Assume that the function req are asynchronous and takes a callback as well. 
Pass a parameter to your function. Format your as a determined signature as a and req
*/
}

Kameron_Hilpert34 answered on · Accepted Answer · 2019-07-09T10:26:01.007Z

Kameron_Hilpert34 answered on July 9th 19 at 10:26

Solution

Add a module to callback

createExtraData function() {
regionsLists.getRegionsList(function(regionList){
console.log(regionList);
sendData();
});
}