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Added threshold option to reduce impact on CDNs and servers #214

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Merged
merged 2 commits into from
Jun 18, 2021
Merged

Added threshold option to reduce impact on CDNs and servers #214

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2c38f7d
Added `threshold` option to allow users select the % of link areas th…
verlok Dec 16, 2020
d0fcb89
Merge branch 'master' into feature/threshold
verlok Jun 18, 2021
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6 changes: 6 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -131,6 +131,12 @@ Default: `Infinity`

The _total_ requests that can be prefetched while observing the `options.el` container.

#### options.threshold
Type: `Number`<br>
Default: `0`

The _area percentage_ of each link that must have entered the viewport to be fetched, in its decimal form (e.g. 0.25 = 25%).

#### options.throttle
Type: `Number`<br>
Default: `Infinity`
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4 changes: 4 additions & 0 deletions src/index.mjs
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Expand Up @@ -49,6 +49,7 @@ function isIgnored(node, filter) {
* @param {Array|RegExp|Function} [options.ignores] - Custom filter(s) that run after origin checks
* @param {Number} [options.timeout] - Timeout after which prefetching will occur
* @param {Number} [options.throttle] - The concurrency limit for prefetching
* @param {Number} [options.threshold] - The area percentage of each link that must have entered the viewport to be fetched
* @param {Number} [options.limit] - The total number of prefetches to allow
* @param {Number} [options.delay] - Time each link needs to stay inside viewport before prefetching (milliseconds)
* @param {Function} [options.timeoutFn] - Custom timeout function
Expand All @@ -63,6 +64,7 @@ export function listen(options) {

const [toAdd, isDone] = throttle(options.throttle || 1/0);
const limit = options.limit || 1/0;
const threshold = options.threshold || 0;

const allowed = options.origins || [location.hostname];
const ignores = options.ignores || [];
Expand Down Expand Up @@ -113,6 +115,8 @@ export function listen(options) {
}
}
});
}, {
threshold
});

timeoutFn(() => {
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24 changes: 23 additions & 1 deletion test/quicklink.spec.js
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Expand Up @@ -274,7 +274,7 @@ describe('quicklink tests', function () {
expect(ours).to.include(`https://example.com/?url=${server}/3.html`);
expect(ours).to.include(`https://example.com/?url=${server}/4.html`);
});

it('should delay prefetch for in-viewport links correctly (UMD)', async function () {
const responseURLs = [];
page.on('response', resp => {
Expand Down Expand Up @@ -303,4 +303,26 @@ describe('quicklink tests', function () {
expect(responseURLs).to.include(`${server}/4.html`);
});

it('should consider threshold option before prefetching (UMD)', async function () {
const responseURLs = [];
page.on('response', resp => {
responseURLs.push(resp.url());
});

await page.goto(`${server}/test-threshold.html`);
await page.setViewport({
width: 1000,
height: 800,
});
await page.waitFor(1000);
expect(responseURLs).to.be.an('array');
expect(responseURLs).to.include(`${server}/1.html`);
expect(responseURLs).to.include(`${server}/2.html`);
await page.evaluate(_ => {
window.scrollBy(0, window.innerHeight);
});
await page.waitFor(400);
expect(responseURLs).to.include(`${server}/3.html`);
expect(responseURLs).to.include(`${server}/4.html`);
});
});
53 changes: 53 additions & 0 deletions test/test-threshold.html
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@@ -0,0 +1,53 @@
<!DOCTYPE html>
<html>

<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>Prefetch: Basic Usage</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" media="screen" href="main.css">
<style>
ul {
display: flex;
flex-wrap: wrap;
justify-content: space-evenly;
}

li {
margin-bottom: 32px;
}

a {
display: block;
width: 400px;
height: 600px;
background: #ccc;
text-align: center;
}
</style>
<script src="https://polyfill.io/v3/polyfill.min.js?features=IntersectionObserver"></script>
</head>

<body>
<ul>
<li>
<a href="1.html">Link 1</a>
</li>
<li>
<a href="2.html">Link 2</a>
</li>
<li>
<a href="3.html">Link 3</a>
</li>
<li>
<a href="4.html">Link 4</a>
</li>
</ul>
<script src="../dist/quicklink.umd.js"></script>
<script>
quicklink.listen({threshold: 0.5});
</script>
</body>

</html>