Simple, pure JavaScript HTTP Get function (QML, IE8+, Chrome, Safari, Firefox, PhoneGap/Cordova)

javascript-ajax-get.js

/**
 * GET contents of a URL
 * @access private
 * @param {string} url - url to get
 * @param {function} error - function to call if there is an error
 * @param {function} callback - function to call if success
 * @returns {void}
 */
function httpGet(url, error, callback) {

    var xhr = new XMLHttpRequest();

    xhr.open('GET', url);
    xhr.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
    xhr.setRequestHeader('Content-Type', 'application/json');
    xhr.onreadystatechange = function() {
        if (xhr.readyState === 4) {
            if (xhr.status === 200 || (xhr.status === 0 && xhr.responseText !== '')) {
                callback({
                    url: url,
                    status: 200,
                    body: JSON.parse(xhr.responseText)
                });
            }
            else {
                error({
                    url: url,
                    status: xhr.status,
                    body: JSON.parse(xhr.responseText)
                });
            }
        }
    };

    xhr.send();
}

qml-use-javascript-ajax-get.js

import 'javascript-ajax-get.js' as HttpRequest

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")
  
    property var response: undefined
    property int responseCode: 0
  
    signal responseReceived()

    Component.onCompleted: {
      
        // Send the request when rendering finishes
        HttpRequest.httpGet("https://api.github.com/repos/symboxtra/jenkins-discord-webhook/releases/latest",
            function(obj) {
                responseCode = obj.status;
                response = obj.body;
                ResponseReceived();
            },
            function(obj) {
                responseCode = obj.status;
                response = obj.body;
                ResponseReceived();
            }
        );

    }
  
    onResponseReceived: {

        if (responseCode !== 200) {
          console.log("Response returned code: " + responseCode);
          return; 
        }
        
        console.log("Response received!");

        // Do stuff with the response object
        console.log(response.url);

    }
}

use-javascript-ajax-get.js

httpGet("https://api.github.com/repos/symboxtra/jenkins-discord-webhook/releases/latest",
    function(obj) {
        alert("Response " + obj.status + ": \n" + JSON.stringify(obj.body, undefined, 4));
    },
    function(obj) {
        alert(JSON.stringify(obj.body, undefined, 4));
    }
);