Add Element#evaluate_async_script

lib/capybara/node/element.rb

@@ -381,6 +381,24 @@ module Capybara
         JS
       end
 
+      ##
+      #
+      # Evaluate the given JavaScript in the context of the element and obtain the result from a
+      # callback function which will be passed as the last argument to the script. `this` in the
+      # script will refer to the element this is called on
+      #
+      # @param  [String] script   A string of JavaScript to evaluate
+      # @return [Object]          The result of the evaluated JavaScript (may be driver specific)
+      #
+      def evaluate_async_script(script, *args)
+        session.evaluate_async_script(<<~JS, self, *args)
+          (function (){
+            #{script}
+          }).apply(arguments[0], Array.prototype.slice.call(arguments,1));
+        JS
+      end
+
+
       def reload
         if @allow_reload
           begin

lib/capybara/spec/session/node_spec.rb

@@ -497,6 +497,21 @@ Capybara::SpecHelper.spec "node" do
     end
   end
 
+  describe "#evaluate_async_script", requires: %i[js es_args] do
+    it "should evaluate the given script in the context of the element" do
+      @session.visit('/with_js')
+      el = @session.find(:css, '#with_change_event')
+      expect(el.evaluate_async_script("arguments[0](this.value)")).to eq('default value')
+    end
+
+    it "should support returning elements after asynchronous operation" do
+      @session.visit('/with_js')
+      change = @session.find(:css, '#change') # ensure page has loaded and element is available
+      el = change.evaluate_async_script("var cb = arguments[0]; setTimeout(function(el){ cb(el) }, 100, this)")
+      expect(el).to eq(change)
+    end
+  end
+
   describe '#reload', requires: [:js] do
     context "without automatic reload" do
       before { Capybara.automatic_reload = false }

spec/shared_selenium_session.rb

@@ -273,7 +273,7 @@ RSpec.shared_examples "Capybara::Session" do |session, mode|
         expect(@animation_session).to have_no_link('transition me away', wait: 0.5)
       end
 
-      it "should disable CSS animations", :focus_ do
+      it "should disable CSS animations" do
         @animation_session.visit('with_animation')
         @animation_session.click_link('animate me away')
         expect(@animation_session).to have_no_link('animate me away', wait: 0.5)