Using Javascript variables to store Ruby Output from <%= %>

Question

@tag is a string.

Why does this work:

tag_tracker = "<%= @tag %>";
alert(tag_tracker);

But not this?

tag_tracker = <%= @tag %>; // Why is this not read as a string?
alert(tag_tracker);

Thank you in advance!

Answer 1

If you have JS inside of ERB files, you need to ensure that the javacript code that is generated is correct.

Let's assume that you have a string "div" stored in @tag

The first option:

tag_tracker = "<%= @tag %>";
alert(tag_tracker);

will generate a correct JS with div wrapped in quotes.:

tag_tracker = "div";
alert(tag_tracker);

The second one:

tag_tracker = <%= @tag %>;
alert(tag_tracker);

will generate JS without quotes around the div :

tag_tracker = div;
alert(tag_tracker);

and that is incorrect, because in this case div is interpreted as a variable, not as string.