client side includes via javascript
Simply include csi.min.js in your <head> and add a data-include attribute on any valid HTML element. csi.js will fetch the value of that attribute, and replace the element with the fetched document.
If, include-me.html looked like this:
<h1>Hello, world!</h1>
Then, a document like this:
<body>
<div data-include="include-me.html"></div>
</body>
would end up rendering like this:
<body>
<h1>Hello, world!</h1>
</body>
csi.js also works from the filesystem, enabling front end developers to splice HTML for back end implementations without the need of running a local HTTP server or copying files to a remote environment for testing to leverage server side includes.
The only caveat is Chrome, which restricts access to local files via AJAX. To resolve this, simply add --allow-file-access-from-files to your Chrome runtime. All other modern browsers work on direct files without any hassle. csi.js also works fine from any web server, assuming you are following appropriate CORS policies.