from 2010 to now...

Client Side Rendering is Not So Easy

Nuria Ruiz

@pantojacoder

What is client side rendering?

To move rendering to the client you need two things.

A Template Engine

Templates

<div class="entry"> <h1>{{title}}</h1> <div class="body"> {{{value}}} </div></div>

{ title : "Pretty Thing",value : "33"

}

Loads of Javascript in the client.

WARNING !!!!

About 1 billion page requests every day.

10% on IE7

0.5% on IE6

Data from 2011

We had a loading bar.

We have a thick Javascript client.

We offer several languages: Spanish, English, Catalan...

Back to loads of Javascript in the client...

Remember that loading bar?

500 K compressed, 23 requests ~

3300 K of Javascript !!!!

Performance Problem #1

Eager loading of Javascript.

Async !=Lazy

Templates were plain HTML documents.

Performance Problems #2 and #3

<div class="footer"><div> <a class="hide" href="%sectionLink%"> <fw:translate id="Video.video_view_more">

%(video_view_more_link)View more... </fw:translate> </a> </div></div>

We needed to do ajax to retrieve templates, which were HTML docs (cannot use <script>).

andLoads of walking the DOM to insert data.

StepBACK

With as much Javascript we had in the client nothing is going to go fast.

Fact #1

We need to load Javascript lazily.

How does the YUI lazy loading work?

<a href="#m=Albums&amp;func=index" onclick= "Bootloader('t-albums','Request('?m=Albums&func=index')) ; return false; " title= "My photo albums"> … </a>

Each link does an HTTP request to retrieve the Javascript needed.

YUI().use('t-albums')

We can remove the loading bar.

Fact #2

We need to start from scratch on the template engine.

Works using a Lexical Parser.

Based on Jison, a Javascript parser generator.

<div class="entry"> <h1>{{title}}</h1> <div class="body"> {{{body}}} </div></div>

Template:

$ npm install handlebars$ /usr/bin/handlebars sample_template.js

Builds a grammar based on HTMLthat compiles to Javascript.

Compilation:

(function() { var template = Handlebars.template; templates['sample_template.js'] = template(

function (Handlebars,depth0,helpers,partials,data) { helpers = helpers || Handlebars.helpers; var self = this; buffer += "<div class=\"entry\">\n <h1>"; stack1 = helpers.title || depth0.title;

..... } buffer += escapeExpression(stack1) + "</h1>\n <div class=\"body\">\n "; .... buffer += escapeExpression(stack1) + "\n </div>\n </div>\n"; return buffer;

});})()

No MoreDOM manipulation

Why Handlebars?

If-Else constructors Precompilation Actively Worked on.

How do we download templates?

With YUI, just like anything else, templates now are Javascript.

<a href="#m=Photo&amp;func=index" onclick="Bootloader('t-photo','Request('?m=Photo&func=index'));return false;" title="My photos">…</a>

YUI walks the dependency tree.

Translations client-side

{{{translate "Photos" "%(photo_save_title)Save"}}}

Do we use Client Side Rendering for everything?

No

Features that exist ONLY client side, like overlays, autocomplete, spinners, chat UI.

Features for which there are significant CPU savings to be done, e.g. high traffic pages like photos.

Last Thoughts.

Do not think about problemsin isolation.

Use the right tool for the job.

Measure Everything.

5 times faster

Questions?