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var Preloader = /** @constructor */ function() {
var DOWNLOAD_ATTEMPTS_MAX = 4;
var progressFunc = null;
var lastProgress = { loaded: 0, total: 0 };
var loadingFiles = {};
this.preloadedFiles = [];
function loadXHR(resolve, reject, file, tracker) {
var xhr = new XMLHttpRequest;
xhr.open('GET', file);
if (!file.endsWith('.js')) {
xhr.responseType = 'arraybuffer';
}
['loadstart', 'progress', 'load', 'error', 'abort'].forEach(function(ev) {
xhr.addEventListener(ev, onXHREvent.bind(xhr, resolve, reject, file, tracker));
});
xhr.send();
}
function onXHREvent(resolve, reject, file, tracker, ev) {
if (this.status >= 400) {
if (this.status < 500 || ++tracker[file].attempts >= DOWNLOAD_ATTEMPTS_MAX) {
reject(new Error("Failed loading file '" + file + "': " + this.statusText));
this.abort();
return;
} else {
setTimeout(loadXHR.bind(null, resolve, reject, file, tracker), 1000);
}
}
switch (ev.type) {
case 'loadstart':
if (tracker[file] === undefined) {
tracker[file] = {
total: ev.total,
loaded: ev.loaded,
attempts: 0,
final: false,
};
}
break;
case 'progress':
tracker[file].loaded = ev.loaded;
tracker[file].total = ev.total;
break;
case 'load':
tracker[file].final = true;
resolve(this);
break;
case 'error':
if (++tracker[file].attempts >= DOWNLOAD_ATTEMPTS_MAX) {
tracker[file].final = true;
reject(new Error("Failed loading file '" + file + "'"));
} else {
setTimeout(loadXHR.bind(null, resolve, reject, file, tracker), 1000);
}
break;
case 'abort':
tracker[file].final = true;
reject(new Error("Loading file '" + file + "' was aborted."));
break;
}
}
this.loadPromise = function(file) {
return new Promise(function(resolve, reject) {
loadXHR(resolve, reject, file, loadingFiles);
});
}
this.preload = function(pathOrBuffer, destPath) {
if (pathOrBuffer instanceof ArrayBuffer) {
pathOrBuffer = new Uint8Array(pathOrBuffer);
} else if (ArrayBuffer.isView(pathOrBuffer)) {
pathOrBuffer = new Uint8Array(pathOrBuffer.buffer);
}
if (pathOrBuffer instanceof Uint8Array) {
this.preloadedFiles.push({
path: destPath,
buffer: pathOrBuffer
});
return Promise.resolve();
} else if (typeof pathOrBuffer === 'string') {
var me = this;
return this.loadPromise(pathOrBuffer).then(function(xhr) {
me.preloadedFiles.push({
path: destPath || pathOrBuffer,
buffer: xhr.response
});
return Promise.resolve();
});
} else {
throw Promise.reject("Invalid object for preloading");
}
};
var animateProgress = function() {
var loaded = 0;
var total = 0;
var totalIsValid = true;
var progressIsFinal = true;
Object.keys(loadingFiles).forEach(function(file) {
const stat = loadingFiles[file];
if (!stat.final) {
progressIsFinal = false;
}
if (!totalIsValid || stat.total === 0) {
totalIsValid = false;
total = 0;
} else {
total += stat.total;
}
loaded += stat.loaded;
});
if (loaded !== lastProgress.loaded || total !== lastProgress.total) {
lastProgress.loaded = loaded;
lastProgress.total = total;
if (typeof progressFunc === 'function')
progressFunc(loaded, total);
}
if (!progressIsFinal)
requestAnimationFrame(animateProgress);
}
this.animateProgress = animateProgress; // Also exposed to start it.
this.setProgressFunc = function(callback) {
progressFunc = callback;
}
};
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