Skip to content
A nano-sized preconnect hint wrapper.
JavaScript HTML
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
dist
src Initial release. Jul 21, 2019
test Initial release. Jul 21, 2019
.editorconfig
.eslintrc.json Initial release. Jul 21, 2019
.gitignore
.npmignore
README.md Breaking caches on these size labels. Jul 21, 2019
http.js
package-lock.json
package.json Initial release. Jul 21, 2019
rollup.config.js

README.md

preconnect

A nano-sized preconnect hint wrapper.

ES5 (.js) version

Uncompressed gzip Brotli

ES6 (.mjs) version

Uncompressed gzip Brotli


preconnect is a very small script that allows you to programmatically invoke a preconnect hint to any host to mask connection latency. The script is designed so that you can invoke this hint whenever is appropriate for your application.

Installing

Since preconnect is Just JavaScript™, you can install it with npm as a production dependency:

npm i preconnect --save

If you're not the npm type, grab one (or both) of the minified versions in this repo's dist folder. There are two minified versions:

  • preconnect.min.js is the Babel-fied ES5 build. It assigns a variable named preconnect on the window.
  • preconnect.min.mjs is the untransformed minified ES6 build. Its default export is a single eponymously named function.

Usage

import preconnect from "preconnect";

const preconnecter = new preconnect({
  // Injects `dns-prefetch` hints in addition to `preconnect` hints
  getDns: true
});

// Preconnects to a link as the user hovers over it
document.getElementById("some-link").addEventListener("mouseover", event => {
  preconnecter.add(event.target.href);
}, {
  // Execute this event handler code only once avoid multiple injections of hints
  once: true
});

In the above example, an early connection is established to the host specified in an <a> element's href value. This could potentially speed up navigation to that host for the user, improving the perceived performance of the navigation.

Options

When you instantiate a new instance of preconnect, you can pass in an options object. There are currently only two options:

  • getDns (default: false)
    Inject a dns-prefetch hint in addition to a preconnect hint. Some browsers don't support preconnect, but some of those browsers do support dns-prefetch. Enabling this ensures those browsers still receive some kind of benefit.
  • timeout (default: 0)
    This script can use requestIdleCallback to take advantage of idle browser time. This helps to reduce monopolization of the main thread so that the page is more responsive to user input. This option specifies, in milliseconds, the deadline by which requestIdleCallback must inject the resource hint elements into the document <head>. A value of 0 (also the default value) disables the use of requestIdleCallback entirely.

Contributing

If you'd like to contribute, please file an issue first so we can discuss. Because I'd like to keep this script very small and simple, new features aren't likely to be added unless the weight they add can be justified.

Author info

My name is Jeremy Wagner. I'm an independent web performance consultant who works with individuals and businesses to help make their sites faster through auditing and/or engineering services. I also write about web stuff, and sometimes I even get to occasionally talk about web stuff. I also ramble on Twitter @malchata.

You can’t perform that action at this time.