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 passing my array:

"graphit([<%=@mpg_values.join(",") %>])"

This produces this in the HTML

"graphit([#&lt;Mile:0x6ff0cf0&gt;,#&lt;Mile:0x6ff0c18&gt;,#&lt;Mile:0x6ff0b58&gt;])"

Which are not the values, they should be decimal numbers. I assume this is because it is a reference to the array so that I why I am getting the messed up values. If I do something like to_s I see the values but it has other stuff like the table and filed name in there as well.

Anybody know how I can get this rails array to a javascript function as an array?

Thanks in advance for any help.

@Ankit Soni when I use to_json I get this [{"mile":{"mpg":"17.156136063144"}},{"mile":{"mpg":"19.06539208592"}},{"mile":{"mpg":"18.471164309032"}}] so I get the extra mile and mpg like in to_s. I suppose I can parse this out in javascript but I would think there would be a simpler method to doing this. — Xaxum
– Xaxum, Commented Aug 25, 2011 at 20:48
How about just calling @mpg_values.inspect? I think the format it returns is the same as a JS array. — ankit
– ankit, Commented Aug 25, 2011 at 20:51
@Ankit-Soni That seems to do the same thing as to_s gives me this.. [#<Mile mpg: #<BigDecimal:6ded698,'0.1715613606 3144E2',16(20)>>, — Xaxum
– Xaxum, Commented Aug 25, 2011 at 21:00

bokor · Accepted Answer · 2012-05-07 20:58:31Z

82

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

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

answered May 7, 2012 at 20:58

bokor

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3 Comments

DanFritz Over a year ago

Thanks alot for this answer, I was looking for it all over!

Aamir Sarwar Over a year ago

In my case no need to add []. Rails will add it. So var js_array = <%= raw @object.to_json %>; is fine for me. It may help someone

Cryptex Technologies Over a year ago

That is the great solution

Joshua Pinter · Accepted Answer · 2015-04-02 05:28:06Z

1

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.

answered Apr 2, 2015 at 5:28

Joshua Pinter

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Comments

Xaxum · Accepted Answer · 2012-11-01 03:24:46Z

0

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.

answered Nov 1, 2012 at 3:24

Xaxum

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1 Comment

Joshua Pinter Over a year ago

I needed to return a specific array as JSON as well. I refactored your method and posted an answer to help others.

Tim B. · Accepted Answer · 2017-10-08 11:36:57Z

0

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

var js_array = #{object};

answered Oct 8, 2017 at 11:36

Tim B.

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CoderMiguel · Accepted Answer · 2020-01-28 19:34:00Z

0

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 %>');

answered Jan 28, 2020 at 19:34

CoderMiguel

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