What is the best way to create a seamless Asynchronous loop?

Question

What is the best way to create a seamless Asynchronous loop?

Adhering to the traditional REST standards, I have divided my resources into separate endpoints and calls. The primary focus here revolves around two main objects: List and Item (with a list containing items as well as additional associated data).

For instance, if a user wishes to retrieve their lists, they could execute a Get request to api/Lists.

Subsequently, the user might also want to access the items within a specific list by making a Get call to api/ListItems/4, where '4' is extracted from List.listId retrieved in the previous request.

All seems to be functioning smoothly so far: utilizing the options.complete attribute of $.ajax enables me to reference a callback method, thereby streamlining these processes.

However, matters become considerably more convoluted when aiming to extract elements for all lists at once. For example, implementing a hypothetical library function known as makeGetRequest which accepts the endpoint and callback function would lead to clearer code. Yet, attempting to fetch 3 elements in a simplistic manner results in:

var success1 = function(elements){
    var success2 = function(elements){
       makeGetRequest("api/ListItems/3", finalSuccess);
    }
    makeGetRequest("api/ListItems/2", success2);
}
makeGetRequest("api/ListItems/1", success1);

Unsightly! This would typically warrant reprimand in an introductory programming course followed by guidance towards loops. But how can one employ a loop in this scenario without relying on external storage?

for(var i : values){
    makeGetRequest("api/ListItems/" + i, successFunction);
}

function successFunction(items){
    //I am invoked multiple times, each time handling only one list's set of items!
}

Even with storage mechanisms in place, it becomes necessary to ascertain when all requests have concluded and acquired their respective data before triggering a master function to compile and process the aggregate information.

Is there a tried and true approach for tackling such situations? Surely, this must have been resolved countless times prior...

javascript ajax rest loops asynchronous

Answer 1

Answer №1

One way to handle multiple endpoint parameters is by creating a stack:

var params = [];
var results [];

params.push({endpoint: "api/ListItems/1"});
params.push({endpoint: "api/ListItems/2"});
params.push({endpoint: "api/ListItems/3"});
params.push({endpoint: "api/ListItems/4"});

You can then implement recursion in your success handler like this:

function fetchData(endPoint) {

   var options = {} // Ajax Options
   options.success = function (data) {
       if (params.length > 0) {
           results.push({endpoint: endpoint, data: data});
           fetchData(params.shift().endpoint);
       }
       else {
          processResults(results)
       }
   }

   $.get(endPoint, options)
}

To start the process, you just need to make a single call:

fetchData(params.shift().endpoint);

Update:

If you prefer to keep everything contained within a function and avoid global scope, you can use the following approach with a callback:

function fetchAllResources(callback) {

    var endpoints = [];
    var results [];

    endpoints.push({endpoint: "api/ListItems/1"});
    endpoints.push({endpoint: "api/ListItems/2"});
    endpoints.push({endpoint: "api/ListItems/3"});
    endpoints.push({endpoint: "api/ListItems/4"});

    function fetchData(endPoint) {
        var options = {} // Ajax Options
        options.success = function (data) {
           if (endpoints.length > 0) {
               results.push({endpoint: endpoint, data: data});
               fetchData(endpoints.shift().endpoint);
           }
           else {
              callback(results)
           }
        }
       $.get(endPoint, options)
    }

    fetchData(endpoints.shift().endpoint);

}

Example of how to use it:

fetchAllResources(function(data) {
   // Process the retrieved data here
});

Answer 2

One way to handle multiple endpoint parameters is by creating a stack:

var params = [];
var results [];

params.push({endpoint: "api/ListItems/1"});
params.push({endpoint: "api/ListItems/2"});
params.push({endpoint: "api/ListItems/3"});
params.push({endpoint: "api/ListItems/4"});

You can then implement recursion in your success handler like this:

function fetchData(endPoint) {

   var options = {} // Ajax Options
   options.success = function (data) {
       if (params.length > 0) {
           results.push({endpoint: endpoint, data: data});
           fetchData(params.shift().endpoint);
       }
       else {
          processResults(results)
       }
   }

   $.get(endPoint, options)
}

To start the process, you just need to make a single call:

fetchData(params.shift().endpoint);

Update:

If you prefer to keep everything contained within a function and avoid global scope, you can use the following approach with a callback:

function fetchAllResources(callback) {

    var endpoints = [];
    var results [];

    endpoints.push({endpoint: "api/ListItems/1"});
    endpoints.push({endpoint: "api/ListItems/2"});
    endpoints.push({endpoint: "api/ListItems/3"});
    endpoints.push({endpoint: "api/ListItems/4"});

    function fetchData(endPoint) {
        var options = {} // Ajax Options
        options.success = function (data) {
           if (endpoints.length > 0) {
               results.push({endpoint: endpoint, data: data});
               fetchData(endpoints.shift().endpoint);
           }
           else {
              callback(results)
           }
        }
       $.get(endPoint, options)
    }

    fetchData(endpoints.shift().endpoint);

}

Example of how to use it:

fetchAllResources(function(data) {
   // Process the retrieved data here
});

Answer 3

Answer №2

dmck's suggestion is likely the top choice. Alternatively, you could consider implementing a bulk list feature for your API to handle requests such as api/ListItems/?id=1&id=2&id=3.

Another possibility is creating an API search endpoint, if that aligns better with your preferred design aesthetic.

Answer 4

dmck's suggestion is likely the top choice. Alternatively, you could consider implementing a bulk list feature for your API to handle requests such as api/ListItems/?id=1&id=2&id=3.

Another possibility is creating an API search endpoint, if that aligns better with your preferred design aesthetic.

What is the best way to create a seamless Asynchronous loop?

Answer №1

Answer №2

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