What is an RJS template?

What is an RJS template? It is simply a file, stored in the app/views hierar-
chy, with an .rjs extension. It contains commands that emit JavaScript to the
browser for execution. The template itself is resolved the same way that .rhtml
templates are: when an action request is received, the dispatcher tries to find
a matching .rhtml template. If the request came in from XHR, the dispatcher
will preferentially look for an .rjs template. The template is parsed, JavaScript
is generated and returned to the browser, where it is finally executed.
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回头再看，理解更深刻。优先渲染rjs文件，很重要。