Ruby variable in JavaScript throws syntax error

Question

I have a Rails controller action that initializes this variable:

@print_url = new_batch_batch_content_template_path(@batch, @content_template)

I tried to access it in an ERB template, as "Using Ruby variable in Javascript (In App View)" says I can do, so I tried:

<script type="text/javascript" charset="utf-8">
  var url = <%= @print_url  %>;
</script>

However, Chrome's console gives me this error:

Uncaught SyntaxError: Invalid flags supplied to RegExp constructor '13'

As you can see, it gets interpreted by JavaScript as a regular expression because it is not evaluated as a string. Why isn't Ruby evaluating this as a string? I don't understand why the example in the other link works but why mine does not.

“Why isn't ruby evaluating this as a string?” – the context of the error is not Ruby, it’s JavaScript. And how do we write text literals in JS again …? — C3roe
– C3roe, Commented Sep 12, 2014 at 23:08
@CBroe you are right, but at the time, I was expecting that value to be already parsed as string before it was rendered in javascript. — Donato
– Donato, Commented Sep 13, 2014 at 1:37
Whether or not ruby parsed it as a string doesn’t matter here – JavaScript is the context that you are introducing the value into here, and therefor you have to treat it according to the syntax rules of that context. — C3roe
– C3roe, Commented Sep 13, 2014 at 1:52

Gergo Erdosi · Accepted Answer · 2014-09-12 23:07:40Z

1

You need to use quotes around the value:

<script type="text/javascript" charset="utf-8">
  var url = '<%= @print_url  %>';
</script>

answered Sep 12, 2014 at 23:07

Gergo Erdosi

42.3k21 gold badges122 silver badges95 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Ruby variable in JavaScript throws syntax error

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related