Namespace pollution

By default, the Google Closure compiler and, by extension, the ClojureScript compiler assume that they control the global Javascript namespace. When using external JavaScript libraries in conjunction with :optimizations simple or :optimizations :advanced, this can cause problems, as the short names the compiler chooses for JavaScript functions often collide with those used in JavaScript libraries.

For example, with advanced optimizations, Closure picks two-letter combinations like window.fb and window.dt, clobbering functions defined in popular frameworks. This results in hard-to-trace JavaScript errors. What's more, these problems can appear seemingly out of the blue as the result of unrelated changes which accidentally affect Closure's naming scheme.

When working with boot-cljs, the solution is to set the :output-wrapper compiler option to true. For example, your main.edn may look like this:

{:require  [app.core]
 :init-fns [app.core/main]
 :compiler-options {:optimizations :advanced
                    :output-wrapper true}}

See the Google Closure FAQ item and the ClojureScript wiki for more details.

Note that currently :output-wrapper true cannot be used with :optimizations :whitespace (ticket).