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PERF: avoid traversing DOM in loadScript

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Once a script is loaded operation should be very fast.

This optimisation avoids a DOM traverse and call to getURL on
every invocation.
This commit is contained in:
Sam Saffron 2020-05-25 18:19:47 +10:00
parent 505122bb45
commit 48fb354bce
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GPG Key ID: B9606168D2FFD9F5
1 changed files with 17 additions and 10 deletions
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27
app/assets/javascripts/discourse/app/lib/load-script.js
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@ -45,34 +45,40 @@ export default function loadScript(url, opts) {
opts = opts || {};
if (_loaded[url]) {
return Promise.resolve();
}
// Scripts should always load from CDN
// CSS is type text, to accept it from a CDN we would need to handle CORS
url = opts.css ? Discourse.getURL(url) : Discourse.getURLWithCDN(url);
const fullUrl = opts.css
? Discourse.getURL(url)
: Discourse.getURLWithCDN(url);
$("script").each((i, tag) => {
const src = tag.getAttribute("src");
if (src && src !== url && !_loading[src]) {
if (src && src !== fullUrl && !_loading[src]) {
_loaded[src] = true;
}
});
return new Promise(function(resolve) {
// If we already loaded this url
if (_loaded[url]) {
if (_loaded[fullUrl]) {
return resolve();
}
if (_loading[url]) {
return _loading[url].then(resolve);
if (_loading[fullUrl]) {
return _loading[fullUrl].then(resolve);
}
let done;
_loading[url] = new Promise(function(_done) {
_loading[fullUrl] = new Promise(function(_done) {
done = _done;
});
_loading[url].then(function() {
delete _loading[url];
_loading[fullUrl].then(function() {
delete _loading[fullUrl];
});
const cb = function(data) {
@ -82,17 +88,18 @@ export default function loadScript(url, opts) {
done();
resolve();
_loaded[url] = true;
_loaded[fullUrl] = true;
};
if (opts.css) {
ajax({
url: url,
url: fullUrl,
dataType: "text",
cache: true
}).then(cb);
} else {
// Always load JavaScript with script tag to avoid Content Security Policy inline violations
loadWithTag(url, cb);
loadWithTag(fullUrl, cb);
}
});
}