Work with several requests to the server [Asynchrony] SetTimeOut, Promises ...?

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Work with several requests to the server [Asynchrony] SetTimeOut, Promises ...?

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I am working with several AJAX requests, some to PHP, others to txt ...

The problem comes when working with the data returned from these requests to form something together (like a table). How can I work with all the information at once?

Investigating a bit I found this article that I recommend your reading that basically gives me two solutions:

CallBacks

Promises

Callbacks seem like a sloppy and terribly inefficient solution, but the promises are really interesting but even trying out examples I do not know how to use them.

I'll give you a quick example where I'm trying it:

window.onload = function(){
 var global="nulisimo";
 var global_segundo="nulisimo_2";

 //Cargo el primer TXT 
 cargar_txt();
 var global = procesar_txt();

 //Cargo el segundo TXT
 cargar_txt_segundo();
 var global_segundo = procesar_txt_segundo();

 setTimeout(function(){
 console.log("Global primera :",global);
 console.log("Global segunda :",global_segundo);
 }, 2000);

Promise.all([procesar_txt(), procesar_txt_segundo()])
.then(resultArray => console.log("Valores globales :",global,"/",global_segundo))
.catch(e => console.log('Error capturado:  ${e}'));

}

Loading TXT is the AJAX request itself, and the only answer it contains is this:

function procesar_txt() {
if(peticion_http.readyState == 4) 
{
    if(peticion_http.status == 200) 
    {
        var cadena = peticion_http.responseText;
        console.log("La cadena en el 1 es  :",cadena);
        return cadena;


    }
  }
}

I can not get back the values of the functions, neither by CallBacks nor by promise. Any idea or example of how to handle the results of several AJAX requests? PD: Is the correct way to treat answers with return?

Thank you very much.

javascript ajax

asked by Roarca 31.03.2018 в 16:56

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1 answer

error MtSQL 1048 can not be null Return to a page after sending a message with sweet alert

score 0 · Accepted Answer

From what I've seen in the code, I've noticed that the functions you pass to Promise.all([]) do not resolve any promises.

The Promise.all([]) method receives an iterable of promises, with which each of your requests must return a promise, in this way the Promise.all([]) method will solve when each of the functions it receives are found.

I show you a similar example.

var procesar_txt = function() {
  return new Promise(function(resolve, reject) {
    setTimeout(function() {
      resolve('RESUELTA PRIMERA PETICIÓN');
    }, 2000);
  })
}

var procesar_txt_segundo = function() {
  return new Promise(function(resolve, reject) {
    setTimeout(function() {
      resolve('RESUELTA SEGUNDA PETICIÓN');
    }, 5000);
  })
}

//Cargo el primer TXT 

Promise.all([procesar_txt(), procesar_txt_segundo()])
  .then((result) => {
    alert(result.join(','));

  })
  .catch(e => alert('Error capturado:  ${e}'));

It's almost your own code, only that I've added a promise to each function.