#Shrub Router

Shrub is a minimal clientside router that gracefully degrades without Javascript. Shrub is only 3KB gzipped and allows you to:

• implement clientside navigation with almost no configuration,
• fall back to full server side routing so that everything still works without Javascript,
• keep all your HTML on the server side and avoid bundling your HTML into your .js files, and
• avoid using a large framework like vue-router.

Normally, when you click links on a page, your browser navigates to the linked page, which reloads the entire page. You might not the entire page to reload — for example, maybe you want a music player to keep playing. A clientside router allows your users to navigate between pages without having to reload the entire page. Instead of having the browser navigate to a different page, the clientside router loads that page on its own, in this case with a fetch() request to the server for the new HTML, and replaces the old HTML with the new HTML.

#Implementation Details

Shrub intercepts all click events and tries to determine whether that click would result in navigation. In simple terms, this means adding some special behaviour when <a> elements are clicked, when a <button> is clicked inside a <form>, and so on.

When such a navigating click is intercepted, Shrub will figure out which URL the action would navigate to, for example the href on an <a>, or the action on a <form>. Shrub will then make a request to that page using fetch().

When using a clientside router, it's usually desirable to be able to only navigate the main content of the page, not to replace the HTML of the entire page. Shrub does this by identifying the body of the old page and the body of the new page, and replacing the former with the latter. Shrub does this by looking for a <main> element — remember that there can only be one <main> tag per page. Therefore, everything in the old <main> will be replaced with the new <main> from the fetched page. This means that you don't need to serve the body of the page at some specific template URL — Shrub will simply make a request for the new page at the usual URL the user would normally navigate to.

#Usage

First, npm install shrub-router. You can then import and initialise it:

import ShrubRouter from 'shrub-router'
ShrubRouter.init();

You need to tell Shrub about which routes you want to be handled. Any routes that you don't tell Shrub about will not be intercepted. When the user clicks on these non-intercepted routes, the browser will navigate normally, reloading the page.

To add routes that replace the page body with the fetched page, use ShrubRouter.add():

ShrubRouter.add('/');
ShrubRouter.add('/about');
ShrubRouter.add('/about/details');

If you want to perform a custom action when a route is navigated to, specify a handler to replace the default one:

ShrubRouter.add('/contact', () => {
	document.write("Hello world");
});

You can remove a route with ShrubRouter.remove('/contact').

There is one important thing to note related to the initialisation of Javascript included in the page. Normally, you would want to run your Javascript code when the page has loaded, by adding a listener for DOMContentLoaded or by placing your code at the bottom of your HTML. When using Shrub, you obviously want your code to be not only on the initial page load, but also when a page is navigated to. Therefore, you should place all of your in-page Javascript code within an event listener for shrub:loaded:

window.addEventListener('shrub:loaded', () => {
	PetiteVue.createApp({
		name: 'Timmy',
	}).mount();
});

#Useful Notes

When making requests for pages using fetch(), Shrub adds a Shrub-Router: true header, which you can use to add custom behaviour for requests made by Shrub on the server side.

#Limitations

The interception of click events could be further improved:

• Clicks on <input type="submit"> elements should be intercepted
• Clicks on <button type="button"> elements should not be intercepted. A button with type="button" inside a form should not submit the form, hence should not navigate, and therefore should not be intercepted at all.

Some new features could be added for ease of use:

• Users that want Shrub to intercept navigation for all pages should be allowed to specify this instead of manually calling .add(). This would give Shrub a truly zero-configuration option.

#Acknowledgements

Written by Vlad-Stefan Harbuz.

MIT-licensed.

Originally based on Pinecone Router, which is MIT-licensed.