Implemented getOutputElementType (openvinotoolkit#25760)

Implemented Method on c++ side.
Updated typescript definitions.
Created unit tests.
For Issue
[https://github.com/openvinotoolkit/openvino/issues/25406](https://github.com/openvinotoolkit/openvino/issues/25406)

Resolved merge errors

---------

Co-authored-by: Alicja Miloszewska <alicja.miloszewska@intel.com>

Author: Pey-crypto

src/bindings/js/node/include/model_wrap.hpp

@@ -108,6 +108,13 @@ class ModelWrap : public Napi::ObjectWrap<ModelWrap> {
      * @return Napi::Array containing a shape of requested output.
      */
     Napi::Value get_output_shape(const Napi::CallbackInfo& info);
+    
+    /**
+     * @brief Helper function to access model output elements types.
+     * @return Napi::String representing the element type of the requested output.
+     *
+     */
+    Napi::Value get_output_element_type(const Napi::CallbackInfo& info);
 
 private:
     std::shared_ptr<ov::Model> _model;

src/bindings/js/node/lib/addon.ts

@@ -234,6 +234,11 @@ interface Model {
    * It returns the number of the model outputs.
    */
   getOutputSize(): number;
+  /**
+   * It gets the element type of a specific output of the model.
+   * @param index The index of the output.
+   */
+  getOutputElementType(index: number): string;
   /**
    * It gets the input of the model.
    * If a model has more than one input, this method throws an exception.

src/bindings/js/node/src/model_wrap.cpp

@@ -7,6 +7,7 @@
 #include "node/include/errors.hpp"
 #include "node/include/helper.hpp"
 #include "node/include/node_output.hpp"
+#include "node/include/type_validation.hpp"
 
 ModelWrap::ModelWrap(const Napi::CallbackInfo& info)
     : Napi::ObjectWrap<ModelWrap>(info),
@@ -25,6 +26,7 @@ Napi::Function ModelWrap::get_class(Napi::Env env) {
                         InstanceMethod("setFriendlyName", &ModelWrap::set_friendly_name),
                         InstanceMethod("getFriendlyName", &ModelWrap::get_friendly_name),
                         InstanceMethod("getOutputShape", &ModelWrap::get_output_shape),
+                        InstanceMethod("getOutputElementType", &ModelWrap::get_output_element_type),
                         InstanceAccessor<&ModelWrap::get_inputs>("inputs"),
                         InstanceAccessor<&ModelWrap::get_outputs>("outputs")});
 }
@@ -171,3 +173,19 @@ Napi::Value ModelWrap::get_output_shape(const Napi::CallbackInfo& info) {
         return info.Env().Undefined();
     }
 }
+
+Napi::Value ModelWrap::get_output_element_type(const Napi::CallbackInfo& info) {
+    std::vector<std::string> allowed_signatures;
+    try {
+        if (ov::js::validate<int>(info, allowed_signatures)) {
+            auto idx = info[0].As<Napi::Number>().Int32Value();
+            const auto& output = _model->output(idx);
+            return cpp_to_js<ov::element::Type_t, Napi::String>(info, output.get_element_type());
+        } else {
+            OPENVINO_THROW("'getOutputElementType'", ov::js::get_parameters_error_msg(info, allowed_signatures));
+        }
+    } catch (const std::exception& e) {
+        reportError(info.Env(), e.what());
+        return info.Env().Undefined();
+    }
+}

src/bindings/js/node/tests/unit/model.test.js

@@ -112,3 +112,48 @@ describe('Model.getOutputSize()', () => {
     assert.strictEqual(model.getOutputSize(), 1, 'Expected getOutputSize to return 1 for the default model');
   });
 });
+
+describe('Model.getOutputElementType()', () => {
+  it('should return a string for the element type ', () => {
+    const result = model.getOutputElementType(0);
+    assert.strictEqual(typeof result, 'string',
+      'getOutputElementType() should return a string');
+  });
+
+  it('should accept a single integer argument', () => {
+    assert.throws(() => {
+      model.getOutputElementType();
+    }, /'getOutputElementType' method called with incorrect parameters/,
+     'Should throw when called without arguments');
+
+    assert.throws(() => {
+      model.getOutputElementType('unexpected argument');
+    }, /'getOutputElementType' method called with incorrect parameters/,
+    'Should throw on non-number argument');
+
+    assert.throws(() => {
+      model.getOutputElementType(0, 1);
+    }, /'getOutputElementType' method called with incorrect parameters/,
+    'Should throw on multiple arguments');
+
+    assert.throws(() => {
+      model.getOutputElementType(3.14);
+    }, /'getOutputElementType' method called with incorrect parameters/,
+    'Should throw on non-integer number');
+  });
+
+  it('should return a valid element type for the default model', () => {
+    const elementType = model.getOutputElementType(0);
+    assert.ok(typeof elementType === 'string' && elementType.length > 0,
+      `Expected a non-empty string, got ${elementType}`);
+  });
+
+  it('should throw an error for out-of-range index', () => {
+    const outputSize = model.getOutputSize();
+    assert.throws(
+      () => { model.getOutputElementType(outputSize); },
+      /^Error: /,
+      'Should throw for out-of-range index'
+    );
+  });
+});