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Stop javascript from implicitly converting string to int

So I have a datapoint object with fields date(string) and count(integer). I'm trying to add them to arrays with some JS inside of my show view. Everything is working well - except that my date string is being converted to a series of JS arithmetic. For example: a value of "2015-05-05" is getting converted to 2005. Code follows:
<h1 id="chart"></h1>
<script language="javascript" type="text/javascript">
var counts = ['Count']
var dates = ['x']
<% #chart.datasource.datapoints.each do |c| %>
dates.push( <%= c.date %> )
counts.push( <%= c.count %> )
<% end %>
chart(counts, dates);
</script>

You're missing quotes:
var counts = ['Count']
var dates = ['x']
<% #chart.datasource.datapoints.each do |c| %>
dates.push( "<%= c.date %>" )
counts.push( <%= c.count %> )
<% end %>
chart(counts, dates);
Wrapping the value in quotes will force JS to consider it as a string primitive, rather than a number and arithmetic operators.

How to add in else statement in underscore template

I have the following code:
var c = 'Credits: <% if (credits) { %> <%= credits %> <% } %> <% else { %> N/A <% } %>'
However I get Unexpected token else. Is the else statement different than how the if statement is added? What should the above correctly be?

Just get rid of the %> <% between } and else. Like this:
var c = 'Credits: <% if (credits) { %> <%= credits %> <% } else { %> N/A <% } %>';
Alternatively, the ternary operator is one of my faves:
var c = 'Credits: <%= credits ? credits : "N/A" %>';
In case it's unclear, the ternary is basically a reduced if/else statement. The part before the ? is the expression being evaluated for truthiness. If it's truthy, the middle part between ? and : is executed, but if it's falsey, the last part after : is executed instead.

A better way to do this would be with the OR operator:
var c = 'Credits:</b> <%= credits || "No credits" %></div>

Javascript map from java map

I want to create a javascript map from a java map to set a dropdown value depending upon the value selected in another dropdown.
Below is the code(not working):
var categoryAndReportsMap = new Object();
<%
Map<String,Set<String>> categoryAndReportsJ = (Map<String,Set<String>>) request.getAttribute("categoryAndReports");
for(Map.Entry<String,Set<String>> e : categoryAndReportsJ.entrySet()){ %>
categoryAndReportsMap[ <% e.getKey(); %> ] = <% e.getValue(); %>;
<% } %>
Please suggest how can I achieve this.

You need quotes around the keys and values :
categoryAndReportsMap["<%= e.getKey() %>"] = "<%= e.getValue() %>";
But this supposes those strings don't contain quotes themselves. The best solution would be to use a JSON serializer like the excellent gson, this would be as simple as
var categoryAndReportsMap = <%= gson.toJson(categoryAndReportsJ) %>;

Rails + JS - Using instance variable (array of arrays with strings)

I have the following in a html.erb file:
<%= #location_list = [['test',2]] %>
<script type="text/javascript">
var test = <%= #location_list.to_json %>
alert(test);
</script>
And the alert is not showing up.
However if I do <%= #location_list = [[3,2]] %> - The alert is showing up.
Why?

<%= %> tag means output something. In your case, you probably dont want to output anything, so I guess you are looking for
<% #location_list = [['test',2]] %>, which means normal statement no output will be involved
Sorry, havn't really answer your question.
var test = <%= #location_list.to_json %>
should be
var test = "<%=j #location_list.to_json %>"

How can I return javascript from a Ruby on Rails helper method?

I have a Note model, which can contain have either an image link attachment (linktype = "image" or some text (linktype = "text). When I display the notes, the method of display changes depending on the linktype. An example is:
<% #notes.each do |q| %>
<h2 class="title"><%= q.name %></h2>
<% if q.linktype == "other"%>
<script type="text/javascript">some javascript</script>
<% elsif q.linktype == "text"%>
<%= q.text %>
<% elsif q.linktype == "image"%>
<img src="<%= q.link %>" />
<% end %>
<% end %>
I have to display the notes in a few different views in my site, so rather than have to repeat the viewing code multiple times, I want to have it in one place and refer to it from different views.
My initial thought was to put the display code in a helper, something like this:
<% #notes.each do |q| %>
note_display(q.linktype, q.link)
<% end %>
But some of the displaying involves javascript (line 4 in first code block). Can I still use a helper method, even though I would need it to return javascript? If so, how do I do it? Thanks for reading.

There's nothing special about javascript, you can return it from helpers as you would return other html content. The only thing I would suggest is to use helpers for tags like
image_tag(q.link)
javascript_tag("some javascript")
content_tag("h2", q.name, :class => "title")

As far as ERB is concerned, JavaScript is just string content like anything else rendered by a template. So your helper method can just construct and return a string:
def note_display(note)
content = ''
content << content_tag('h2', h(note.name), :class => 'title')
if note.linktype == 'other'
content << javascript_tag("some javascript")
elsif note.linktype == 'text'
content << h(note.text)
elsif note.linktype == 'image'
content << image_tag(note.link)
end
content
end
You can use this helper method using:
<% #notes.each do |n| %>
<%= note_display(n) %>
<% end %>