In JavaScript how do I/should I use async/await with XMLHttpRequest?

Question

Full disclosure: I\'d qualify myself as having intermediate JavaScript knowledge. So this is slightly above my experience level at this time.

I\'ve got a Google Chro

Answer 1

You can for example create an asynchronous class to use instead of the original one. It lacks some methods but it can serve as an example.

(function() {
    "use strict";
    
    var xhr = Symbol();
    
    class XMLHttpRequestAsync {
        constructor() {
            this[xhr] = new XMLHttpRequest();
        }
        open(method, url, username, password) {
            this[xhr].open(method, url, true, username, password);
        }
        send(data) {
            var sxhr = this[xhr];
            return new Promise(function(resolve, reject) {
                var errorCallback;
                var loadCallback;
                
                function cleanup()  {
                    sxhr.removeEventListener("load", loadCallback);
                    sxhr.removeEventListener("error", errorCallback);
                }
                
                errorCallback = function(err) {
                    cleanup();
                    reject(err);
                };
                
                loadCallback = function() {
                    resolve(xhr.response);
                };
                
                
                sxhr.addEventListener("load", loadCallback);
                sxhr.addEventListener("error", errorCallback);
                
                
                sxhr.addEventListener("load", function load() {
                    sxhr.removeEventListener("load", load);
                    resolve(sxhr.response);
                });
                sxhr.send(data);
            });
        }
        set responseType(value)
        {
            this[xhr].responseType = value;
        }
        setRequestHeader(header, value) {
            this[xhr].setRequestHeader(header, value);
        }
    }
    
    addEventListener("load", async function main() {
        removeEventListener("load", main);


        var xhra = new XMLHttpRequestAsync();
        xhra.responseType = "json";
        xhra.open("GET", "appserver/main.php/" + window.location.hash.substring(1));
        console.log(await xhra.send(null));
        
    });
    
}());