handlebars & namespaces

class overview

  • Homework solution
  • Handlebars
  • Namespaces
  • JavaScript constructors
  • The 'this' keyword
  • jQuery event handlers
  • Controlling time in JS
  • Homework overview

HANDLEBARS

  • Roughly follows the Mustache specification
  • Provides a super-easy way to create dynamic html with JavaScript objects.
  • Store your templates in your html.
  • Include Handlebars by downloading, Bower, or cdn.
  • <script src="http://cdnjs.cloudflare.com/ajax/libs/handlebars.js/2.0.0-alpha.2/handlebars.min.js"></script>
  •  How to render a template with an object
 
 var rawTemplate = $('#itemTemplate').html(); var compiledTemplate = Handlebars.compile(rawTemplate); var finishedHtml = compiledTemplate(obj); $('#items').append(finishedHtml);

HANDLEBARS TEMPLATES

Template:
<script id="itemTemplate" type="text/x-handlebars-template">   <div class="header">{{title}}</div>   <div class="body">       <div>{{type}}</div>
       <div>{{price}}</div>   </div></script>
Object:
 var product = {     title : "Cheese",     type : "Sharp Cheddar",     price : "$3.49" }

HANDLEBARS BLOCKS

  • Blocks create looping or conditional behavior
  • Typically used to determine whether properties exist or for accessing sub-arrays.
  • If block:
 
 {{#if type}}    <div>Type: {{type}}</div> {{else}}    <div>Type: None</div> {{/if}}
  • Each block:
 {{#each products}}    <div>{{title}}</div>    <div>{{price}}</div> {{/each}}

HANDLEBARS HELPERS

  • Enables you to create your own custom tags with behavior.
  • Useful for formatting & custom html behavior
  • Think about redesigning your objects before creating a new helper.
  • Register a helper in JS. First arg is name, second is a function to determine output. Can take arguments.
 
 Handlebars.registerHelper('formatMoney', function(arg1) {    return Handlebars.SafeString('$' + arg1);});
  • Using it in your Handlebars template:
 {{formatMoney price}} //price is a property from your object

namespaces

  • Very useful for organizing code & abstracting ideas.
  • Namespaces use Object literal declaration.
    • Can't make new objects from it.
    • Shouldn't hold state.
    • Good for utility functions, static properties.
  • Why use Namespaces?
    • Keeps Global scope clean.
    • Adds context to your functions.
    • Allows you to cleanly share any code.

TYPICAL CODE ORGANIZATION

  • Declarations first.
    • Objects/Variables
    • Functions
  • Code to actually run comes last.

Object Constructors

  • jsbin examples
  • Allow you to create reproducible Objects
  • Can use instanceof to check Object type
  • Perfect for Objects that hold state
  • Enables use of the 'this' keyword inside a function
  • Used when you are creating a multiple objects that will have the same structure but different contents.
//constructor declarationfunction CustomObject() {};//using constructor to create an objectvar myObj = new CustomObject();myObj instanceof CustomObject;// > true

this

  • Reserved keyword
  • The 'this' variable always refers to the current object.
  • Works in functions that are constructors, but not normal functions.




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AJS Lecture 6: Handlebars & Namespaces

By Ryan Lewis

AJS Lecture 6: Handlebars & Namespaces

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