Underscore Template with Ruby Backend not working - ruby-on-rails

Question

I am using the underscore template to create a template for making bootstrap dropdown menus. The code worked fine on my own computer, but now I'm adding it to a ruby on rails backend server. Now the code no longer works. I was told the code in between the <% %> is interpreted as ruby code instead of javascript. I don't know ruby at all, but someone showed me how to write a for loop.
<!-- Dropdown Menu-->
<script type="text/template" id="dropdown">
<div class="dropdown">
<a class="dropdown-toggle" data-toggle="dropdown">
<span> <%= name %> </span>
<b class="caret"></b>
</a>
<ul class="dropdown-menu">
<% array_of_items.each do |obj| %>
<li> <a> <%= obj %> </a> </li>
<% end %>
</ul>
</div>
</script>
The error I get is "Undefined variable array_of_items" Of course it's not defined, I define it later on
this.$el.append(this.makeDropdown({
name: this.name,
array_of_items: [1,2,3,4]
}));
The underscore template works like this for Javascript, but for Ruby it will not allow me to have an undefined variable in a template for some reason, What can I do?

Answer 1

So the problem I think is here:
<% array_of_items.each do |obj| %>
Rails is interpreting this as ERB, and as there's no variable declared in Ruby, you're getting the error. Try adding your JS code into the asset pipeline perhaps?

Answer 2

Javascript's and ruby's variable are in quite different 'scopes';
here <% array_of_items %> should be defined as a template local variable:
<% array_of_items = [1,2] %>
<%= array_of_items %>
<script>
document.body.innerHTML += array_of_items;
array_of_items = ['j', 's'];
document.body.innerHTML += array_of_items;
// var from js + var from ruby
document.body.innerHTML += array_of_items + <% array_of_items %>; // #=> should be smth like `js12`
</script>