Rails 3 passing a rails array to javascript function which uses a javascript array

Question

I am trying to pass a rails array to a javascript function. The function will then use the array values in javascript so I need to keep it an array.

Here is how I am

Answer 1

bokor's answer works, but causes some linter and IDE errors if you want the array to be saved to a const, instead of a var / let.

The following variation seems to work and be compliant with the linters and IDEs that I am using.

const js_array = JSON.parse('<%= raw @object %>');

Answer 2

Going to JSON as suggested a couple times in this post always gave me something like this.

[{"mile":{"date":"2011-05-20","mpg":"18.565887006952"}},{"mile":{"date":"2011-06-01","mpg":"18.471164309032"}}]

What I really wanted was just this... [[2011-05-20, 18.56][2011-06-01, 18.47]]

So I handled it with a helper like so.

  def chart_values()
    @chart_values = '['
    @mpg_values.each do |m|
      @chart_values = @chart_values+'['+m.date.to_s+', '+m.mpg.round(2).to_s+'],'
    end
    @chart_values = @chart_values+']'
  end

Then passed chart_values() to the javascript.

Likely not the best solution but it gave me the desired values in the format I needed.

Answer 3

If you're using HAML, you can just do this:

var js_array = #{object};

Answer 4

Use Ruby's collect Method.

A cleaner version of your solution, Xaxum, would be something like this:

def chart_values
  @mpg_values.collect do |mpg_value|
    [ mpg_value.date.to_s, mpg_value.mpg.round(2).to_f ]
  end
end

The collect method automatically generates an array of whatever the block results in, so you'll end up with something like this:

[ 
  [2011-05-20, 18.56], 
  [2011-06-01, 18.47]
]

I also changed the mpg value to use to_f, which provide a number instead of a string.

Answer 5

Since this still seems like an issue and nobody resolved it. Here goes

var js_array = [<%= raw @object.to_json %>];