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const load = {
cache_bust: path => {
let url = new URL(path, location.origin);
url.href += (url.href.includes("?")) ? '&' : '?';
// The `Number` type in Javascript, when interpreted as an integer, can only
// safely represent [-2^53 + 1, 2^53 - 1] without the loss of precision [1].
// We do not generate a global value and increment from it, as the increment
// might not have enough precision to be reflected.
//
// [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number
url.href += "unique=" + Math.random().toString().substring(2);
return url.href;
},
image_with_attrs: async (path, attribute_map) => {
return new Promise(resolve => {
const img = new Image();
if (attribute_map instanceof Object) {
for (const [key, value] of Object.entries(attribute_map)) {
img[key] = value;
}
}
img.onload = img.onerror = resolve;
img.src = load.cache_bust(path);
});
},
// Returns a promise that settles once the given path has been fetched as an
// image resource.
image: path => {
return load.image_with_attrs(path, undefined);
},
// Returns a promise that settles once the given path has been fetched as a
// font resource.
font: path => {
const div = document.createElement('div');
div.innerHTML = `
<style>
@font-face {
font-family: ahem;
src: url('${load.cache_bust(path)}');
}
</style>
<div style="font-family: ahem;">This fetches ahem font.</div>
`;
document.body.appendChild(div);
return document.fonts.ready.then(() => {
document.body.removeChild(div);
});
},
stylesheet_with_attrs: async (path, attribute_map) => {
const link = document.createElement("link");
if (attribute_map instanceof Object) {
for (const [key, value] of Object.entries(attribute_map)) {
link[key] = value;
}
}
link.rel = "stylesheet";
link.type = "text/css";
link.href = load.cache_bust(path);
const loaded = new Promise(resolve => {
link.onload = link.onerror = resolve;
});
document.head.appendChild(link);
await loaded;
document.head.removeChild(link);
},
// Returns a promise that settles once the given path has been fetched as a
// stylesheet resource.
stylesheet: async path => {
return load.stylesheet_with_attrs(path, undefined);
},
iframe_with_attrs: async (path, attribute_map, validator) => {
const frame = document.createElement("iframe");
if (attribute_map instanceof Object) {
for (const [key, value] of Object.entries(attribute_map)) {
frame[key] = value;
}
}
const loaded = new Promise(resolve => {
frame.onload = frame.onerror = resolve;
});
frame.src = load.cache_bust(path);
document.body.appendChild(frame);
await loaded;
if (validator instanceof Function) {
validator(frame);
}
document.body.removeChild(frame);
},
// Returns a promise that settles once the given path has been fetched as an
// iframe.
iframe: async (path, validator) => {
return load.iframe_with_attrs(path, undefined, validator);
},
script_with_attrs: async (path, attribute_map) => {
const script = document.createElement("script");
if (attribute_map instanceof Object) {
for (const [key, value] of Object.entries(attribute_map)) {
script[key] = value;
}
}
const loaded = new Promise(resolve => {
script.onload = script.onerror = resolve;
});
script.src = load.cache_bust(path);
document.body.appendChild(script);
await loaded;
document.body.removeChild(script);
},
// Returns a promise that settles once the given path has been fetched as a
// script.
script: async path => {
return load.script_with_attrs(path, undefined);
},
// Returns a promise that settles once the given path has been fetched as an
// object.
object: async (path, type) => {
const object = document.createElement("object");
const loaded = new Promise(resolve => {
object.onload = object.onerror = resolve;
});
object.data = load.cache_bust(path);
if (type) {
object.type = type;
}
document.body.appendChild(object);
const timeout = new Promise(r => step_timeout(() => {
console.log("Timeout was reached before load or error events fired");
r();
}, 2000));
await Promise.race([loaded, timeout]);
document.body.removeChild(object);
},
// Returns a promise that settles once the given path has been fetched
// through a synchronous XMLHttpRequest.
xhr_sync: async (path, headers) => {
const xhr = new XMLHttpRequest;
xhr.open("GET", path, /* async = */ false);
if (headers instanceof Object) {
for (const [key, value] of Object.entries(headers)) {
xhr.setRequestHeader(key, value);
}
}
xhr.send();
},
xhr_async: path => {
const xhr = new XMLHttpRequest();
xhr.open("GET", path)
xhr.send();
return new Promise(resolve => {
xhr.onload = xhr.onerror = resolve;
});
}
};
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