What is x-tmpl?

javascript

template-engineering

variable-interpolation

browser-caching

byAnton Shumikhin·Mar 12, 2025

x-tmpl is a type identifier for inline HTML templates, preventing direct interpretation by the browser prior to being activated by JavaScript.

Using x-tmpl example:

<!-- HTML structure as mysterious gift, ready to be unwrapped by... JavaScript! -->
<script type="text/x-tmpl" id="tmpl-example">
  <div>Name: {%= name %}</div>
  <div>Age: {%= age %}</div>
</script>

Rendering with JavaScript:

// Knock Knock! Who's there? It's JavaScript, unlocking potential of our HTML gift!
var tmpl = document.getElementById('tmpl-example').innerHTML;
document.body.innerHTML += tmpl.replace(/{%= name %}/g, 'John')
                               .replace(/{%= age %}/g, '30');

Mocks up an HTML within a script tag set as type="text/x-tmpl". Later, JavaScript hones it with dynamic data before ushering it to the page.

Nitty-gritty of `x-tmpl`

x-tmpl promotes separation of the markup assembly line from the dynamic data dispatch, distilling cleaner code and hassle-free maintenance.

Relations: JavaScript and Libraries

Although text/x-tmpl isn't recognized MIME type in any formal specification, it's a convention for front-end templating. With type text/x-tmpl, the browser is signalled to treat the script block as a template markup, not a normal JavaScript.

Using x-tmpl lets templating engines like jQuery File Upload plugin and JavaScript-Templates plugin know where to bind dynamic content.

Importance of `{%...%}`

They are nothing short of magical symbols⚡️, allowing variable interpolation, control logic (loops, conditionals, etc.), and flow management inside the template.

Spotting and navigating potential traps

While manipulating x-tmpl, watch out for obstacles and way around them:

Browser Caching: Use caching strategies like versioning or cache-busting techniques to ensure templates are updated properly with each new version.
XSS Vulnerabilities: Templates could pave way for cross-site scripting attacks if user input is mismanaged. Opt for sanitizing user data before template rendering.
Performance: Hefty templates might weigh down performance. Cut corners by optimizing templates and considering pre-compilation for production environments.

When is `x-tmpl` your pal?

Here are your go-to moments for x-tmpl:

Dynamic content: When user interactions should shape content in real-time.
Reusable components: Need to make unique UI components with different settings? x-tmpl is your best friend.
Single Page Applications (SPAs): For robust templating manipulation of DOM without reloading.

`x-tmpl` best practices

Simplicity: Debugging complex logic in templates can be a pain. Defer logic handling to JavaScript modules.
Escape Data: Treat data as potential hazards. A good defense mechanism? Use functions to escape data before rendering.
Comments: No one appreciates cryptic codes. Use comments for intricate logic, facilitates future maintenance.