Logicful HTML Templates
Interpol is a Logicful Template System. What can you do with it? Stuff like this:
let label = '%0 is a friend of %1'renderPeople(people)<ul>for person in people, friend in person.friends<li>[person.name, friend.name] | label</li>end</ul>endwhen not people<b> 'There are no people to render' </b>end
renderPeople is a partial. Its first form renders a list of interpolated strings resulting from a set of nested loops. The second form is a guarded version that catches the case when there is no
people value or it is empty. How easy is that to do with your current template system? I suspect pretty difficult. Maybe not possible at all.
There has been a lot of noise about logic-less templates in recent years. The sales pitch is that they enforce separation of concerns, so that business logic doesn't taint the presentation layer. Fair enough, I agree, separation of concerns is a good thing.
In reality the separation of concerns is still violated in many cases, except that it's now your business logic that's often tainted with presentation-specific mapping acrobatics to massage your data into a form the template system will accept. You're also having to leverage helpers extensively, backfilling the 'logic' a logic-less template system refused to provide in the first place.
That being the case, what's the benefit of a logic-less template system? None that I can see. Especially when a developer can still choose to separate concerns in their design. And trust me, most developers are smart enough to make that decision on their own. You don't have to force their hands by giving them tools that paint them into a corner.
Interpol lets you decide and makes sure you're not crippled as a result of your decision.
You might ask why the interpolation was so involved. After all, in other systems you could just embed the values directly into the resulting content. You can do something like that in Interpol as well. It would look like this:
person.name 'is a friend of' friend.name
But that approach falls down once you start localizing your application (and you probably will). Interpol was designed with localization in mind. In a real Interpol application, you'd probably define such a
label in a single module of localized strings and then pull them into your template with an
You could have also performed the interpolation using named indexes rather than positional ones:
let label = '%pname is a friend of %fname'# ... and then inside the for loop ...[pname = person.name, fname = friend.name] | label
To use Interpol directly from node.js applications, npm install it like so:
npm install interpol --save
You can then include it in your Node code like so:
var interpol = require'interpol';
npm install interpol-views --save
You can then follow the instructions available at the interpol-views GitHub page.
To add Interpol as a Bower dependency to your project, do the following:
bower install interpol --save
Note: The entry point function for Interpol in the browser is always named
Application bundles can be pre-compiled and automatically registered with Interpol. This will allow you to bypass the loading of the compiler and PEG.js parser. Instead, you can load sets of pre-compiled templates from your server for faster initialization.
Note: The Interpol command-line interface generates pre-compiled bundles. You can install this globally using
npm -g install and can then invoke the tools at your terminal by typing
If you must parse raw templates in the browser, you will need to load the version of Interpol that includes the compiler (and its PEG.js parser).
To compile a raw template into a closure, invoke
interpol(String) as a function. Provide to it a string containing your template:
var compiledTemplate = interpolsomeTemplateString;
console.logcompiledTemplatelist:type: 'task' id: 1 name: 'This is my first task'type: 'story' id: 2 name: 'This is my first story';
Copyright (c) 2014, 2015 Thomas S. Bradford
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