Passing multiple rails variables to javascript

Question

I have some values in ruby (variables and objects / hash) that I want to pass on to javascript on the rendered page. Currently I use these methods to simply write the javascript of declaring the variables at the client end.

  def declare_as_js_vars vars
    string = ""
    vars.each do |name, value|
      string += self.declare_as_js_var(name, value)
    end
    string
  end

  def declare_as_js_var name, value
    name.to_s + "='" + value.to_s + "';"
  end

The problem here is that I am unable to declare objects, and have to declare vars individually. I was wondering if there is some way in rails to easily do this because this is turning out to be quite a hack.

How should I pass variables and objects to javascript? Please provide some syntax example

Solution 1

It' s a bit late but maybe it will help the others. There is a nice gem called gon which is very useful with passing variables from rails to javascript. You can also send the whole object.

In the controller you can have something like this

@your_int = 123
@your_array = [1,2]
@your_hash = {'a' => 1, 'b' => 2}
gon.your_int = @your_int
gon.your_other_int = 345 + gon.your_int
gon.your_array = @your_array
gon.your_array << gon.your_int
gon.your_hash = @your_hash
gon.your_object = Table.find(params[:id])

then in the javascript it will be available like

alert(gon.your_int)
alert(gon.your_other_int)
alert(gon.your_array)
alert(gon.your_hash)
alert(gon.your_object.name)

There is also a railscast about it.

Solution 2

I like to use script tags of type JSON to get the job done. It avoids polluting the global namespace and Rails happens to have great support for serializing objects to JSON.

You might use something like this in you view:

<script id="my_vars_json" type="text/json">
    <%= @my_vars.to_json %>
</script>

Then it's up to you to parse the JSON with JavaScript. I like to use jQuery:

$(function () {

    var myVarsJSON = $("#my_vars_json").html(),
        myVars     = $.parseJSON(myVarsJSON);

    console.log(myVars);

});

Hope that helps!

Solution 3

I needed to get user's first name from database and pass the value to a javascript variable in JSON format.

I then declared a ruby variable named token which takes id and firstname attribute from the user table,

  ActiveRecord::Base.include_root_in_json = false

  @token = User.all.to_json(only: [:id, :firstname])

In the erb file, I used the following line,

var tokenList = <%= @token.html_safe %>

Solution 4

I think using Gon gem will be the best solution. also check out this video casts

View more solutions

Comments

[Eli Hooten]

I had trouble with this approach when @my_vars represented multiple entires from a database (e.g., @my_vars = MyVar.all in the controller, where MyVar is a model). Using <%= raw @my_vars.to_json %> remedied the issue. Thanks for your answer, it was helpful!