✅ Find a way to perform JS's asynchronous call from Crystal

spec/alizarin_spec.cr

@@ -117,7 +117,7 @@ describe "JSCClass" do
 end
 
 describe WebExtension::Chainable do
-  it "works" do 
+  it "works" do
     eval_js <<-JS
       var me = new Person();
       me.set_name("TheEEs").greet();
@@ -126,3 +126,20 @@ describe WebExtension::Chainable do
     ret.should eq "Hello TheEEs"
   end
 end
+
+describe "async" do
+  it "works" do
+    eval_js <<-JS
+      var result = do_it_later(function(result){
+        window.a = "Hello";
+      });
+    JS
+    script_result
+    sleep 0.4
+    eval_js <<-JS
+      window.a;
+    JS
+    ret = String.new JSC.to_string script_result
+    ret.should eq "Hello"
+  end
+end

webExtensions/extension.cr

@@ -14,8 +14,8 @@ class XAML::MyFileReader < File
   end
 end
 
-class Person 
-  INSTANCES = [] of Void* 
+class Person
+  INSTANCES = [] of Void*
   @name = ""
 
   def self.new(params)
@@ -25,7 +25,7 @@ class Person
   @[JSCInstanceMethod]
   @[Chainable]
   def set_name(p)
-    @name = p.first.to_s 
+    @name = p.first.to_s
     Box.box(self)
   end
 
@@ -113,6 +113,19 @@ initialize_extension do
     }
   end)
 
+  do_it_later = function p do
+    sto = JSCContext.get_value("setTimeout").as(JSCFunction)
+    cb = p.first
+    o = JSCObject.new
+    o["c"] = cb
+    sto.call(
+      function pp do
+        o["c"].as(JSCFunction).call
+      end, 0)
+  end
+
+  JSCContext.set_value "do_it_later", do_it_later
+
   JSCContext.set_value "MyFileReader", register_class(XAML::MyFileReader)
   JSCContext.set_value "Person", register_class(Person)
 end