javascript syntax for parameters in the context of rails 6 packs

Question

Action: a javascript action attempting to retrieve data based on two parameters, a user-input one and an issuing page parameter.

whereas in the past something like the following would work:

<%= javascript_tag do %> chart.data = data_<%=j params[:nation_id] %>; <% end %>

now with the javascript being 'packed', the compilation of syntax like <%=j params[:nation_id] %> does not work and returns :

/search.json?nation_id=%22%3C%=j%20params[:nation_id]%20%%3E%22&q=mi 

modifying the packs/muni.js file as follows, also does not generate a proper url for the search function

  var options = {
    url: function(phrase) {
      return '/search.json?nation_id="#{params[:nation_id]}"&q=' + phrase;
    },
    getValue: "name",
  };

returning

/search.json?nation_id=%22

the page is set with /new?top%5Bnation_id%5D=1&commit=Set

How does the javascript pack need to be written?

Answer 1

Javascript pack is not rendered for each request/visitor - whole point is that it is packed once per deploy and is the same for all (except for when you have several packs, dynamic module loading and other advanced techniques, but still code is not changed per request). In fact, older method with asset pipeline is very similar in this aspect.

Do not try using ruby inside the pack, but instead think of a way to pass the parameter to the js code.

For example, you can pass it via a adding some html tag an querying it from javascript: In view:

<meta name="nation_id" content="<%= params[:nation_id] %>" />

in js:

nation_id = document.querySelector('meta[name="nation_id"]').content;
return `/search.json?nation_id=${nation_id}&q=${phrase}`;

PS. also you might need to escape your phrase with encodeURIComponent