phaser/v3/src/loader/XHRLoader.js

var MergeXHRSettings = require('./MergeXHRSettings');

var XHRLoader = function (file, globalXHRSettings)
{
    var config = MergeXHRSettings(globalXHRSettings, file.xhr);

    var xhr = new XMLHttpRequest();

    xhr.open('GET', file.src, config.async, config.user, config.password);

    xhr.responseType = file.xhr.responseType;
    xhr.timeout = config.timeout;

    if (config.header && config.headerValue)
    {
        xhr.setRequestHeader(config.header, config.headerValue);
    }

    if (config.overrideMimeType)
    {
        xhr.overrideMimeType(config.overrideMimeType);
    }

    // After a successful request, the xhr.response property will contain the requested data as a DOMString, ArrayBuffer, Blob, or Document (depending on what was set for responseType.)

    xhr.onload = file.onLoad;
    xhr.onerror = file.onError;
    xhr.onprogress = file.onProgress;

    //  This is the only standard method, the ones above are browser additions (maybe not universal?)
    // xhr.onreadystatechange

    xhr.send();

    return xhr;
};

module.exports = XHRLoader;