Single Page Apps – Writing a LoDash/Underscore Plugin for SammyJS

Sammy.jsAlthough SammyJS is a router that provides you with file loading of data and templates. You load templates and data using Sammy’s plugins.

In this tutorial, you will learn how you can use sammy.load to load JSON data, and then use LoDash (or Underscore) to _.find() to retrieve the item based on the value provided in the sammy route. And you will combine the template and data using a custom Sammy plugin.

Why LoDash?

LoDash or Underscore provide great methods for working with collections and arrays. There are subtle differences in these two libraries. But for this tutorial, they provide the same functionality.

Use these libraries to “slice and dice” your data. In the case of this tutorial, you will use _.find(). In your real life applications, there will be more complex ways of manipulating your data, that LoDash can provide.

LoDash includes _.template(). The template method compiles a set of HTML code and turns it into JavaScript. The templates can include _ and complex JavaScript functions.

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Single Page Apps – Deep Dive into Loading Templates Using Sammy, Mustache, RequireJS

Sammy.jsIn this tutorial you will learn how Sammy renders a Mustache template and then load and interpolate the template. In addition, you will use Sammy and templates as Asynchronous Module Definition (AMD) modules.

The tutorial builds on the previous postings Getting Started with SammyJS – Routes, where you learned you can use Sammy to provide client side routing, and Loading JSON Using Sammy where you learned how to load JSON data using sammy.load().

This tutorial goes beyond the getting started with Sammy tutorial, JSON Store, provided in Sammy’s documentation. In this tutorial you will learn what happens behind the scenes with each of the important calls. The idea is to help you choose the right Sammy calls as your application gets more complex.

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Single Page Apps – Loading JSON Using Sammy

Sammy.jsSingle Page Applications (SPA) are web sites/applications which are consists of single page and provide smooth user experience in contrast with traditional click and refresh web pages. You can integrate data loading along with routing to provide your users with a site or app that “pops”. No waiting, because the data has already been loaded.

We will start with a prototype for a Sammy page, which provides a div whose identifier is main, where we will render the data. And the code to load the scripts.

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Single Page Apps – Displaying Data Using Sammy Plugins Using Mustache

image[4][5]Sammy.js has a lot more to offer than simply defining routes in the app. More advanced users can explore custom events and namespaces, for event-driven applications.

Sammy’s author Aaron and others provide additional functionality for your application. In this tutorial, you’ll get a summary of plugins that are available for Sammy, and then we’ll dive into a few that are important in building our single page applications.

In this post, you will build a single page application that receives JSON data, displays the data in various ways using templates, and stores the data to provide an off line experience. You will use the following plug-ins:

  • Sammy.Mustache. Provides a quick way of using mustache style templates in your app.

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Single Page Apps – Single Page Forms Using the Sammy’s EventContext

image[4]Let’s expand on the previous post Single Page Apps – Getting Started with SammyJS – Routes and create a form using Sammy.js. Instead of adding HTML inline, we can use an external template. And because the data for the input form is contained on a single page, we can display the data on what appears to the user to be another page, after the user submits the form.

Sammy.js helps you create RESTful evented JavaScript single page applications. You can maintain the state of your app with the URL without having to refresh or change the page.

This topic introduces how you can use Sammy.EventContext object. The Sammy.EventContext is created every time a route is run or a bound event is triggered. The callbacks for these events are evaluated within a Sammy.EventContext.

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Single Page Apps – Getting Started with SammyJS – Routes

image[4][3]Single Page Applications (SPA) are web sites/applications which are consists of single page and provide smooth user experience in contrast with traditional click and refresh web pages

Even in the world of high speed broadband internet connections, changing a web page when clicked on a link is not desirable and would certainly be appreciated if possible to avoid. SPA’s provide just that.

Sammy.js helps you create RESTful evented JavaScript single page applications. You can maintain the state of your app with the URL without having to refresh or change the page.

You use a route in your URLs that contains #/operation as part of path name. By changing URL to a hash based path #/pathName you avoid page refresh and your page responds to the new user request. It also makes it possible to use browser back/forward button.

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Single Page App – Loading, Caching LoDash or Underscore Templates Using RequireJS, AppCache

image613As you learned in the previous post, you learned how you can load templates inline in your app using RequireJS. The next step is to load and compile a template file. And for your offline app, learn how you can cache templates. Caching saves a round trip to the server, making your application incredibly responsive.

In this tutorial we will compile, load, and cache LoDash (or Underscore) templates and then use those templates to transform data in our single page app.

The technique uses RequireJS, so there is no more dynamic loading. Templates are bundled within your code which saves some HTTP requests.

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Single Page App – Using RequireJS Asynchronous Module Definition (AMD) Modules with jQuery, LoDash

image6[1]In the previous post, you learned how you can use RequireJS in projects to define your own loading order, and how to build your own modules.

This tutorial go into depth on how to use RequireJS for AMD (Asynchronous Module Definition) modules. You will write we can write our own modules and load them with RequireJS.

In this tutorial you will build a small app that uses LoDash and jQuery. If you want to use Underscore, just substitute Underscore for the LoDash references.

Although you can use a bunch of <script> tags to load the libraries, your page is blocked during the load. And you could minify them and maintain the order in your own code. But with RequireJS, you include the RequireJS source and let it load the files.

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Single Page App – HTML Templates With Logic Using Underscore, LoDash

Underscore.jsUnderscore complement to JavaScript’s standard library. And it also gives you simple templating.

The Underscore template function compiles JavaScript templates into functions that can be evaluated for rendering. Template functions can both interpolate variables or execute arbitrary JavaScript code. That allows you to put more logic than you can with Mustache.

Comparison to Mustache, Handlebars

Mustache and Handlebars are what are known as “logic-less template engines.” With those libraries you cannot include any overly complex logic in the template. You get the most basic control structures needed to output data, keeping the HTML (or other content) clean.

Underscore is different. It’s a JavaScript library in itself, like Prototype or jQuery, and comes with it’s own templating engine. The templates have access to any method or helpers within the library, meaning the templates are strictly tied to JavaScript and house a lot more of the logic.

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Single Page App – Finding Items in JSON Using Underscore or LoDash

Underscore.jsUnderscore is a utility-belt library for JavaScript that provides a lot of the functions and programming support that you would expect in Prototype.js (or Ruby), but without extending any of the built-in JavaScript objects.

Underscore provides 80-odd functions that help you deal with collections, arrays, functions, objects, and more.

You will want Underscore for you non-DOM code or even complex front end code, such as MVC. You can use map, select, invoke or specialized helpers: function binding, JavaScript templating, deep equality testing. Underscore uses built-in functions in modern browsers when you want to use forEach, map, reduce, filter, every, some and indexOf.

Underscore gives you simple templating, too, similar to what you learned about in Object JavaScript – External Templates Using Mustache, jQuery.

You can use Underscore in your Web application or on Node.js.

When minified and GZipped it weighs in at less than 4Kb. Where possible it delegates functionality to native browser implementations for performance. It has no other dependencies and so adds very little overhead to your total script assets. It can be used on the client or server.

In this post, you’ll learn how to use Underscore for finding items in your single page app. You’ll learn how to:

  • Select a group of toys based on price cutoff.
  • Find a toy from its name.
  • Get a sorted list of unique categories.
  • Sort the list of product names.

In a later post, you’ll learn how to create a list of search terms and respond to a search request using JavaScript and Underscore.

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