Accept block in JS::Object.new

This change allows to pass a block to `JS::Object.new` method. The block
will be converted to a function and passed as the last argument to the
constructor.

This idea was originally proposed by @ledsun in #393

packages/gems/js/lib/js.rb

@@ -137,8 +137,10 @@ class JS::Object
   #   JS.global[:Date].new(2020, 1, 1)
   #   JS.global[:Error].new("error message")
   #   JS.global[:URLSearchParams].new(JS.global[:location][:search])
+  #   JS.global[:Promise].new ->(resolve, reject) { resolve.call(42) }
   #
-  def new(*args)
+  def new(*args, &block)
+    args = args + [block] if block
     JS.global[:Reflect].construct(self, args.to_js)
   end
 

packages/npm-packages/ruby-wasm-wasi/test/unit/test_object.rb

@@ -245,6 +245,27 @@ class CustomClass {
     assert_equal "hello", JS.global[:CustomClass].new(js_object)[:option1].to_s
   end
 
+  def test_new_with_block
+    ctor = JS.eval <<~JS
+      return function (a, b, c) {
+        this.ret = c(a, b);
+      }
+    JS
+    new_obj = ctor.new(1, 2) { |a, b| a.to_i + b.to_i }
+    assert_equal 3, new_obj[:ret].to_i
+
+    promise = JS.global[:Promise].new do |resolve, reject|
+      resolve.apply 42
+    end
+    value = promise.await
+    assert_equal 42, value.to_i
+
+    promise = JS.global[:Promise].new do |resolve, reject|
+      JS.global.queueMicrotask(resolve)
+    end
+    promise.await
+  end
+
   def test_to_a
     assert_equal [1, 2, 3], JS.eval("return [1, 2, 3];").to_a.map(&:to_i)
     assert_equal %w[f o o], JS.eval("return 'foo';").to_a.map(&:to_s)