CODEWITHSUNDEEP
javascriptjqueryruby-on-railsruby
vimx
vimx

Reputation: 138

Ruby code in a JavaScript function

I'm new in the world of JavaScript, jQuery, and Ajax. I have a JavaScript function where I want to use the value of a JavaScript variable inside of embedded Ruby code. For example, below I want to use the JS p variable as an argument to the Ruby call to @r.search():

$(function (){
  $('#data-select').on('change',function (){
     var p = document.getElementById('data-select').value; 
     alert(<% j @r.search(+ p +) %>);
  });
});

I want to know if i can do this? And if i can what's the syntax?

Upvotes: 2

Views: 9093

Answers (2)

Rob Wise
Rob Wise

Reputation: 5130

First off, I'm assuming this is Ruby on Rails (which you tagged it as). When using ERB you are telling Rails to first evaluate the embedded Ruby code to dynamically insert data that is on the server-side, and then send the file to the client over the internet where their web browser then evaluates the JavaScript.

So if this is what's in your file, and you passed a @user variable with a name method that evaluates to "John Smith":

// test.js.erb
alert("Hello <%= @user.name %>");

When that file is rendered, your server will evaluate it to this:

// test.js
alert("Hello John Smith");

And then send that over the internet to the client. Only once the client's computer has received this file will the JavaScript be evaluated. They (and the JavaScript) will therefore never see the embedded Ruby code. Therefore what you're doing cannot be done the way you have it because the Ruby code is evaluated before the JavaScript can set the p variable.

If you want to get information that resides on the server after the client has received the file and is running the JavaScript, you can use something called Ajax, which uses JavaScript to send data asynchronously back to the server. Check out this Rails guide for more details on that.

Upvotes: 6

Sathish Subramanian
Sathish Subramanian

Reputation: 111

You Can't do it, because while rendering the view all ERb will be converted to HTML or relevant, so you don't have access tp the Ruby objects after rendering the view.

You can also pass the dynamic values from javascript to certain rails methods

Refer: http://apidock.com/rails/ActionView/Helpers/PrototypeHelper/remote_function

But this rails method also will converted to ajax function after rendering.

The solution:

Try to send an ajax request and show the result in view.

Upvotes: 1

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