Challenges encountered when trying to incorporate vanilla JavaScript within a Ruby environment

While working on my controller, I attempted to render vanilla JavaScript but encountered an unexpected outcome. Below is the code snippet:

class UploadController < ApplicationController

    def index

        render :file => 'app\views\upload\uploadfile.rhtml'

    end

    def uploadFile

        render :js => "alert('Hello Rails');"

       post = DataFile.save(params[:upload])

    end

end

Prior to executing post = DataFile.save(params[:upload]), I expected to see an alert box, but instead, I am seeing a download box. What could be causing this issue?

Answer №1

render :js allows you to send data as text/javascript MIME type to browsers, prompting them to either download or display the content. (For example, my browser, Chromium, displays .js files as plaintext.)

render :js is primarily used to return JavaScript code that will be executed by existing code on the page.

For instance, you can make an AJAX call from jQuery:

$.ajax({
  type: "POST",
  url: "tokens/1/destroy.js",
  data: { _method: 'DELETE', cell: dsrc.id }
});

The above snippet is from a personal project. In this scenario, since no dataType is specified, jQuery will make an educated guess based on the returned data's MIME-Type, which is text/javascript, and then execute it. If it were your code, it would trigger an alert dialog.

Essentially, the page must be loaded already and expecting the "vanilla JavaScript" to come back in order for it to work.

If you just need to run some code for a specific action, you can wrap it with javascript_tag in your template/view or include an external .js file.

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