I am using Chart.js as a library to show responsive charts on some websites. One of a cool new features is the tooltip. When using it, you usually have to override its behaviour a little bit. So there is this kind of language you can use:
tooltipTemplate: "<%=label%>:<%= value %>"
You see the problem? Rails tries to interpret the
<%= %> and there is no existing variable in ruby defined. So it throws an error.
The solution I found was clearly easy but hard to find:
use <%% (double %) instead in your erb, then it will skip.
tooltipTemplate: "<%%=label%>:<%%= value %>"