Faster subsequent page-loads by prefetching in-viewport links during idle time
Faster subsequent page-loads by prefetching in-viewport links during idle time
Quicklink attempts to make navigations to subsequent pages load faster. It:
navigator.connection.effectiveType) or has data-saver enabled (using navigator.connection.saveData)<link rel=prefetch> or XHR). Provides some control over the request priority (can switch to fetch() if supported).This project aims to be a drop-in solution for sites to prefetch links based on what is in the user's viewport. It also aims to be small (< 1KB minified/gzipped).
npm install --save quicklink
You can also grab quicklink from unpkg.com/quicklink.
Once initialized, quicklink will automatically prefetch URLs for links that are in-viewport during idle time.
Quickstart:
<!-- Include quicklink from dist -->
<script src="dist/quicklink.umd.js"></script>
<!-- Initialize (you can do this whenever you want) -->
<script>
quicklink.listen();
</script>
For example, you can initialize after the load event fires:
<script>
window.addEventListener('load', () =>{
quicklink.listen();
});
</script>
ES Module import:
import { listen, prefetch } from "quicklink";
The above options are best for multi-page sites. Single-page apps have a few options available for using quicklink with a router:
quicklink.listen() once a navigation to a new route has completedquicklink.listen() against a specific DOM element / componentquicklink.prefetch() with a custom set of URLs to prefetchReturns: Function
A "reset" function is returned, which will empty the active IntersectionObserver and the cache of URLs that have already been prefetched. This can be used between page navigations and/or when significant DOM changes have occurred.
Type: HTMLElement
Default: document.body
The DOM element to observe for in-viewport links to prefetch.
Type: Number
Default: Infinity
The total requests that can be prefetched while observing the options.el container.
Type: Number
Default: Infinity
The concurrency limit for simultaneous requests while observing the options.el container.
Type: Number
Default: 2000
The requestIdleCallback timeout, in milliseconds.
Note: The browser must be idle for the configured duration before prefetching.
Type: Function
Default: requestIdleCallback
A function used for specifying a timeout delay.
This can be swapped out for a custom function like networkIdleCallback (see demos).
By default, this uses requestIdleCallback or the embedded polyfill.
Type: Boolean
Default: false
Whether or not the URLs within the options.el container should be treated as high priority.
When true, quicklink will attempt to use the fetch() API if supported (rather than link[rel=prefetch]).
Type: Array<String>
Default: [location.hostname]
A static array of URL hostnames that are allowed to be prefetched.
Defaults to the same domain origin, which prevents any cross-origin requests.
Important: An empty array ([]) allows all origins to be prefetched.
Type: RegExp or Function or Array
Default: []
Determine if a URL should be prefetched.
When a RegExp tests positive, a Function returns true, or an Array contains the string, then the URL is not prefetched.
Note: An
Arraymay containString,RegExp, orFunctionvalues.
Important: This logic is executed after origin matching!
Type: Function
Default: None
An optional error handler that will receive any errors from prefetched requests.
By default, these errors are silently ignored.
Returns: Promise
The urls provided are always passed through Promise.all, which means the result will always resolve to an Array.
Important: You much
catchyou own request error(s).
Type: String or Array<String>
Required: true
One or many URLs to be prefetched.
Note: Each
urlvalue is resolved from the current location.
Type: Boolean
Default: false
Whether or not the URL(s) should be treated as "high priority" targets.
By default, calls to prefetch() are low priority.
Note: This behaves identically to
listen()'spriorityoption.
quicklink:
IntersectionObserver to be supported (see CanIUse). We recommend conditionally polyfilling this feature with a service like Polyfill.io:<script src="https://polyfill.io/v3/polyfill.min.js?features=IntersectionObserver"></script>
Alternatively, see the Intersection Observer polyfill.
Defaults to 2 seconds (via requestIdleCallback). Here we override it to 4 seconds:
quicklink.listen({
timeout: 4000
});
Defaults to document otherwise.
quicklink.listen({
el: document.getElementById('carousel')
});
prefetch() URLsIf you would prefer to provide a static list of URLs to be prefetched, instead of detecting those in-viewport, customizing URLs is supported.
// Single URL
quicklink.prefetch('2.html');
// Multiple URLs
quicklink.prefetch(['2.html', '3.html', '4.js']);
// Multiple URLs, with high priority
// Note: Can also be use with single URL!
quicklink.prefetch(['2.html', '3.html', '4.js'], true);
Defaults to low-priority (rel=prefetch or XHR). For high-priority (priority: true), attempts to use fetch() or falls back to XHR.
Note: This runs
prefetch(..., true)with URLs found within theoptions.elcontainer.
quicklink.listen({ priority: true });
Provide a list of hostnames that should be prefetch-able. Only the same origin is allowed by default.
Important: You must also include your own hostname!
quicklink.listen({
origins: [
// add mine
'my-website.com',
'api.my-website.com',
// add third-parties
'other-website.com',
'example.com',
// ...
]
});
Enables all cross-origin requests to be made.
quicklink.listen({
origins: true,
// or
origins: []
});
These filters run after the origins matching has run. Ignores can be useful for avoiding large file downloads or for responding to DOM attributes dynamically.
// Same-origin restraint is enabled by default.
//
// This example will ignore all requests to:
// - all "/api/*" pathnames
// - all ".zip" extensions
// - all <a> tags with "noprefetch" attribute
//
quicklink.listen({
ignores: [
/\/api\/?/,
uri => uri.includes('.zip'),
(uri, elem) => elem.hasAttribute('noprefetch')
]
});
You may also wish to ignore prefetches to URLs which contain a URL fragment (e.g. index.html#top). This can be useful if you (1) are using anchors to headings in a page or (2) have URL fragments setup for a single-page application, and which to avoid firing prefetches for similar URLs.
Using ignores this can be achieved as follows:
quicklink.listen({
ignores: [
uri => uri.includes('#')
// or RegExp: /#(.+)/
// or element matching: (uri, elem) => !!elem.hash
]
});
The prefetching provided by quicklink can be viewed as a progressive enhancement. Cross-browser support is as follows:
Set() and Array.from() shims. Projects like es6-shim are an alternative you can consider.Certain features have layered support:
navigator.connection.effectiveType) is only available in Chrome 61+ and Opera 57+{priority: true} and the Fetch API isn't available, XHR will be used instead.A prefetch method can be individually imported for use in other projects.
This method includes the logic to respect Data Saver and 2G connections. It also issues requests thru fetch(), XHRs, or link[rel=prefetch] depending on (a) the isPriority value and (b) the current browser's support.
After installing quicklink as a dependency, you can use it as follows:
<script type="module">
import { prefetch } from 'quicklink';
prefetch(['1.html', '2.html']).catch(err => {
// Handle own errors
});
</script>
Here's a WebPageTest run for our demo improving page-load performance by up to 4 seconds via quicklink's prefetching. A video comparison of the before/after prefetching is on YouTube.
For demo purposes, we deployed a version of the Google Blog on Firebase hosting. We then deployed another version of it, adding quicklink to the homepage and benchmarked navigating from the homepage to an article that was automatically prefetched. The prefetched version loaded faster.
Please note: this is by no means an exhaustive benchmark of the pros and cons of in-viewport link prefetching. Just a demo of the potential improvements the approach can offer. Your own mileage may heavily vary.
Cross-origin prefetching (e.g a.com/foo.html prefetches b.com/bar.html) has a number of limitations. One such limitation is with session-stitching. b.com may expect a.com's navigation requests to include session information (e.g a temporary ID - e.g b.com/bar.html?hash=<>×tamp=<>), where this information is used to customize the experience or log information to analytics. If session-stitching requires a timestamp in the URL, what is prefetched and stored in the HTTP cache may not be the same as the one the user ultimately navigates to. This introduces a challenge as it can result in double prefetches.
To workaround this problem, you can consider passing along session information via the ping attribute (separately) so the origin can stitch a session together asynchronously.
Sites that rely on ads as a source of monetization should not prefetch ad-links, to avoid unintentionally counting clicks against those ad placements, which can lead to inflated Ad CTR (click-through-rate).
Ads appear on sites mostly in two ways:
Inside iframes: By default, most ad-servers render ads within iframes. In these cases, those ad-links won't be prefetched by Quicklink, unless a developer explicitly passes in the URL of an ads iframe. The reason is that the library look-up for in-viewport elements is restricted to those of the top-level origin.
Outside iframes:: In cases when the site shows same-origin ads, displayed in the top-level document (e.g. by hosting the ads themselves and by displaying the ads in the page directly), the developer needs to explicitly tell Quicklink to avoid prefetching these links. This can be achieved by passing the URL or subpath of the ad-link, or the element containing it to the custom ignore patterns list.
Intersection Observer to prefetch all of the links that are in view and provided heavy inspiration for this project.Licensed under the Apache-2.0 license.
FAQs
Faster subsequent page-loads by prefetching in-viewport links during idle time
The npm package quicklink receives a total of 10,213 weekly downloads. As such, quicklink popularity was classified as popular.
We found that quicklink demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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