how to run ruby in haml in javascript definition?

Question

• how can I run ruby code inside javascript in haml?
• if I use var = #{message} in my example I get undefined local variable or method message

Answer 1

First, let's review what you seem to know:

1. Ruby requires you to define local variables before you use them.
2. You can run Ruby code on lines outside of a filter using - ....
3. You use #{...} markup to interpolate Ruby code inside a filter.

You say you want to run each, but presumably you want output from this; since the result of #{...} is turned into a string and put in your code, what you really want (probably) is map:

%html
  %head
    :javascript
      var foo = [];
      #{
        limit = rand(4)+3
        array = (0..limit).to_a
        array.map{ |i| "foo[#{i}] = #{rand(12)};" }.join ' '
      }
      console.log(foo.length);
    %body

Running the above code gives this output:

As you can see, the big #{...} block (which may span multiple lines) runs arbitrary Ruby code. The result of the last expression (in this case the map{...}.join) is converted to a string and placed in the output.