BOOSTING THE
CLIENT-SIDE EVEN MORE WITH
Jan 20th, 2014
AGENDA
- Motivation
- Clientside templating
- Thick Clients
- Thick Clients vs Thick Servers
- Handlebars.js
- Definition
- Why Handlebars?
- How it works
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Boosting the client-side even more with Handlebars
AGENDA
- Handlebars Overview
- The 3 Main Parts of Handlebars Templating
- Syntax
- Built-in Helpers
- Custom Helpers
- Custom Function Helpers
- Custom Block Helpers
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Boosting the client-side even more with Handlebars
pre-requisites
- Javascript: Intermediate level
- HTML: Intermediate level
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Boosting the client-side even more with Handlebars
"My site is living in 2001. I have a pantry full of ajax powered spaghetti, and basically everything is a new page refresh. How can I made it slick?"
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Boosting the client-side even more with Handlebars
Client Side Templating
-
Generating HTML in the Browser
-
Generally used alongside with client side frameworks such as Backbone or Ember
What is client side templating?
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Boosting the client-side even more with Handlebars
Thick client
- What is it?
- 'A computer (client) in client–server architecture that typically provides rich functionality independent of the central server.'
- In other words, it removes some requirements from thick servers.
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Boosting the client-side even more with Handlebars
Thick client Flow
- Server sends Client templates + 'application code'.
- Application code initializes the View.
- As user interacts with the View, JSON data is transferred between client and server.
- Application code applies templates to the data to update the view.
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Boosting the client-side even more with Handlebars
why use thick clients?
Because there are problems with Thick Servers.
THICK Servers VS THICK CLIENTS
-
Server may be overkill.
- Often have a gigantic piece of software to implement an application.
- A lot of overhead due to Content Management System just to display some HTML pages.
- Doesn't take advantage of the browser capabilities.
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Boosting the client-side even more with Handlebars
THICK CLIENTS benefits
- Infrastructure
- Dynamic content can be expensive
- Caching
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Boosting the client-side even more with Handlebars
THICK CLIENTS BENEFITS
- Thick servers works under non-optimal
user experience.
- Why?
- Response times
- 0.1 sec: Instantaneous
- 1 sec: Sticky
- 10 sec: What am I doing with my life?!
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Boosting the client-side even more with Handlebars
MORE THICK CLIENTS Upsides
- Avoids page reloads
- Avoids inefficient architecture
- Better separation of concerns
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Boosting the client-side even more with Handlebars
MORE THICK CLIENTS Upsides
- Avoids coupling
- Avoids ugly clientside code
- "Good architecture allows future features."
- Yehuda Katz
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Boosting the client-side even more with Handlebars
client side Templating BENEFITS
- Avoids HTML generation in JS
- Readable
- Maintainable
- Usable
- Decoupled to the server
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Boosting the client-side even more with Handlebars
Handlebars.JS
- Contributed by Yehuda Kaltz
- Logicless
- Superset of Mustache
- Powerful & extensible
- Fast
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Boosting the client-side even more with Handlebars
DEFINItion
- Handlebars.js is a client-side templating engine for JS.
- Handlebars.js has a compiler built with JS that takes any Handlebars template and compiles them to a JS function.
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Boosting the client-side even more with Handlebars
how it works
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Boosting the client-side even more with Handlebars
when TO use it?
-
Frequent updates to the view, either due to data changes on the server or on the client.
- You have multiple parts of your system dependant on your data from the server, and you want all the parts to process the same data.
- Your application has much interactivity and is very responsive.
- Your application is a single-page app with multiple views.
- You don't want JS code to contain HTML markup.
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Boosting the client-side even more with Handlebars
WHy handlebars ?
- One of the most advanced, feature-rich and popular among all JS template engines (Mustache, Underscore,
EJS, Dust.JS, etc)
- Most active community.
- Used on cutting edge and promising client side frameworks: Meteor.js, Derby.js and Ember.js.
Super easy to be used with Backbone.
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Boosting the client-side even more with Handlebars
Handlebars essentials
- To use Handlebars, first you link to the Handlebars.js file in the head block of your HTML page, just like you do for jQuery or any .js files.
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Boosting the client-side even more with Handlebars
Expressions
-
A simple expression is written like this:
{{ content }} - Or like this, in the case of Handlebars block expressions:
<div> Name: {{ customerName }} </div>
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Boosting the client-side even more with Handlebars
script tags
- Handlebars templates can be embedded in script tags.
- You retrieve the HTML content from the script tag and pass it to the Handlebars compiler.
<script id="header" type="text/x-handlebars-template">
<div> Name: {{ headerTitle }} </div>
</script>
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Boosting the client-side even more with Handlebars
Context
- Contains the data to be displayed on the page.
- Passed as an object to the Handlebars function.
var theData = {
customers: [
{ firstName: ”John”, lastName: ”Doe”, age: 20 },
{ { firstName: ”Chuck”, lastName: ”Norris”, age: 25 }
]
}; <script id="header" type="text/x-handlebars-template">
{{#each customers}}
<li> {{ firstName }} {{ lastName }} </li>
{{/each}}
</script>
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Boosting the client-side even more with Handlebars
the handlebars compile function
- Finally, in order to use our Handlebars template, we need to:
-
Compile it with Handlebars compile function.
It generates a JS function representing that template.
- Invoke that compiled function with our data.
var theTemplate = Handlebars.compile(templateScript);
var html = theTemplate(theData);
$(document.body).append(html);
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Boosting the client-side even more with Handlebars
A Non-Handlebars vs A Handlebars project
HTML File
<html>
<head>
<script type="text/javascript" src="jquery-1.9.1.min.js">
</script>
</head>
<body>
The List of Shoes:
<ul class="shoesNav"></ul>
</body>
</html>
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Boosting the client-side even more with Handlebars
A Non-Handlebars project
JS File$(function() {
var shoesData = [ { name: "Nike", price: 199.00 },
{ name: "Loafers", price: 59.00 },
{ name: "Wing Tip", price: 259.00 } ];
function updateAllShoes(shoes) {
var theHTMLListOfShoes = "";
shoesData.forEach(function(eachShoe) {
theHTMLListOfShoes += '<li class="shoes">' +
'<a href="/' + eachShoe.name.toLowerCase() + '">' +
eachShoe.name + ' -- Price: ' + eachShoe.price +
'</a></li>';
});
return theHTMLListOfShoes;
}
$(".shoesNav").append(updateAllShoes(shoesData));
});
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Boosting the client-side even more with Handlebars
A Handlebars project
$(function() {
var shoesData = [ { name: "Nike", price: 199.00 },
{ name: "Loafers", price: 59.00 },
{ name: "Wing Tip", price: 259.00 } ];
var theTemplateScript = $("#shoe-template").html();
var theTemplate = Handlebars.compile(theTemplateScript);
$(".shoesNav").append(theTemplate(shoesData));
}); <script id="shoe-template" type="x-handlebars-template">
{{#each this}}
<li class="shoes">
<a href="/{{name}}">{{name}} -- Price: {{price}} </a>
</li>
{{/each}}
</script>
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Boosting the client-side even more with Handlebars
syntax
- Expressions
- Blocks
- Paths
- Parent Paths
- Partials (sub-templates)
- Helpers
- Built-in Helpers
- Custom Helpers
- Built-in Helpers
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Boosting the client-side even more with Handlebars
Blocks
- Blocks in Handlebars are expressions within an opening {{# }} followed by a closing {{/ }}.
{{#each}}
Content goes here.
{{/each}}- Here is an if block:
{{#if someValueIsTrue}}
Content goes here
{{/if}}
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Boosting the client-side even more with Handlebars
Paths
-
A path in Handlebars is a property lookup.
var objData = {
name: { firstName: "Michael", lastName:"Jackson" }
} - We can use nested paths to lookup the property you want, like this:
{{name.firstName}}
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Boosting the client-side even more with Handlebars
Partials (Sub-templates)
- Sometimes you want to reuse a template inside a section of another. On this case you just need to invoke the partial expression:
{{> partialName}}
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Boosting the client-side even more with Handlebars
Helpers
- Expressions that provide the necessary logic expressiveness on Handlebars Templates.
- Built-In helpers: provides conditional and loop logic.
- Each
- If
- Else
- Unless
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Boosting the client-side even more with Handlebars
helpers - each
- Used to iterate over an array or object.
var data = {
people: [
"Chuck Norris",
"Bruce Lee",
"Jackie Chan"
] };<script id="peopleTemplate" type="text/x-handlebars-template">
<ul class="people_list">
{{#each people}}
<li>{{this}}</li>
{{/each}}
</ul>
</script>
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Boosting the client-side even more with Handlebars
helpers - EACH
- If the data object passed to the each helper is not an array, the entire object is the current context and we use the this keyword.
var data = {
firstName: "Chuck",
lastName: "Norris"
};<script id="peopleTemplate" type="text/x-handlebars-template">
<ul class="people_list">
{{#each this}}
<li>{{firstName}} {{lastName}}</li>
{{/each}}
</ul>
</script>
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Boosting the client-side even more with Handlebars
helpers - IF
- Works like a regular IF conditional statement, except that it only accepts boolean values.
- The block inside an IF Helper will only be rendered on the case the boolean is true.
var data = {
user: [ "Bond" ]
};<script id="peopleTemplate" type="text/x-handlebars-template">
<ul class="people_list">
{{#if user.length}}
<li>{{user}}</li>
{{/if}}
</ul>
</script>
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Boosting the client-side even more with Handlebars
Custom helpers
- Introduce flexibility on Handlebars.
- They are created in JS code, not inside the templates.
- Custom helpers allow creating any kind of JS logic.
var data = {
firstName: "Chuck",
lastName: "Norris"
};<script id="peoleTemplate" type="text/x-handlebars-template">
<ul class="people_list"> {{#fullName this}}
</ul>
</script> - Output:
<div> Chuck Norris </div>
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Boosting the client-side even more with Handlebars
Custom helpers
- To be used, they need to be registered before all the rest of the Handlebars JS code.
Handlebars.registerHelper('fullName', function(person) {
return person.first + ' ' + person.last;
});
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Boosting the client-side even more with Handlebars
Conclusion
- Thick Clients is not a web trend to be ignored.
- Client-side Templating is a great web solution and worth to give it a try.
- Handlebars is a powerful & great tool for this endeavor.
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Boosting the client-side even more with Handlebars
Learn more
- Official website - handlebarsjs.com
- Javascript.is (Sexy) Blog - Richard of Stanley - javascriptissexy.com/handlebars-js-tutorial-learn-everything-about-handlebars-js-javascript-templating
- Try Handlebars.js right now in your browser - James Fuller - tryhandlebarsjs.com
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Boosting the client-side even more with Handlebars
Assignment
Refactor the multiple-choice quiz code given on the last talks using Handlebars. Keep in mind the following:
- Use and abuse of Handlebars blocks of expressions.
-
Make sure you use the following:
- Handlebars Path (property lookup) - 2x
- A sub-template.
- Each of these built-in Helpers: Each, If, Else, Unless
- A custom helper.
-
Extra:
- Pre-compile your Handlebars template.
- Make use of one Handlebars Parent Path lookup.
- Send me the solution in a GitHub repo.
extra
Parent Path
Parent path ../ allows to lookup properties on parents of the current context.
var shoesData = {
groupName: "Celebrities",
users: [ { name: { first : "John", last: "Doe" } },
{ name: { first : "John", last: "Waters" } } ] };<script id="shoe-template" type="x-handlebars-template">
{{#users}}
<li>
{{name.first}} {{name.last}} is in the {{../groupName}} group
</li>
{{/users}}
</script>Mike Alexander is in the Celebrities group.
John Waters is in the Celebrities group.
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Boosting the client-side even more with Handlebars
Copy of Boosting the client-side even more with Handlebars.js
By Leonardo Dias de Vasconcelos
Copy of Boosting the client-side even more with Handlebars.js
On this talk we will cover concepts of the new web trend - client side templating, comparing with the traditional Thick Server approach, and also go over Handlebars templating language. By Alysson Ferreira
