Accessing Index in #each in emberjs

UPDATE

Since this PR, it's now possible to use the each helper with index, taking advance of the new block params syntax. This is available on canary and hopefully will be enabled by default in ember 1.11

{{#each model as |item index|}}
  <li>
    Index: {{index}} Content: {{item}}
  </li>
{{/each}}

Live sample

FOR OLD VERSIONS

You can use {{_view.contentIndex}}.

{{#each item in model}}
  <li>
    Index: {{_view.contentIndex}} Content: {{item}}
  </li>
{{/each}}

Live sample

Note, regarding the @index syntax specifically, as of October 2014:

Ember does not support @index (or any of the other @data type properties).

https://github.com/toranb/ember-template-compiler/issues/16#issuecomment-38823756

No it doesn't exist in Ember's version of Handlebars, one way is to use an item controller and add a property to it saying whether it's the first or last etc.

App.IndexController = Ember.ArrayController.extend({
  itemController: 'itemer'
});

App.ItemerController = Ember.ObjectController.extend({
  needs:['index'],
  isFirst: function(){
    return this.get('color') === this.get('controllers.index.firstObject.color');
  }.property('controllers.index.firstObject')
});

http://emberjs.jsbin.com/aPewofu/1/edit

I like the answer from @kingpin2k--The Ember Way is to use a controller to decorate a model, and in this context we want to decorate it by adding an index property to represent its place in the collection.

I do it slightly differently, by building a separate collection of instance controllers decorated for the task at hand:

App.PostsIndexController = Ember.ArrayController.extend({
  indexedContent: function() {
    get('content').map(function(item, index) {
      App.PostsItemController.create({
        content: item,
        index: index
      });
    });
  }.property('content')
});

App.PostsItemController = Ember.ObjectController.extend({
  index: null
});