implements bindings for Object.is (#537)

* implements bindings for Object.is

* adds counterpart test cases for non-equal values

crates/js-sys/src/lib.rs

@@ -1712,6 +1712,12 @@ extern "C" {
     #[wasm_bindgen(method, js_name = hasOwnProperty)]
     pub fn has_own_property(this: &Object, property: &JsValue) -> bool;
 
+    /// The Object.is() method determines whether two values are the same value.
+    /// 
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is
+    #[wasm_bindgen(static_method_of = Object)]
+    pub fn is(value_1: &JsValue, value_2: &JsValue) -> bool;
+
     /// The `Object.isExtensible()` method determines if an object is extensible
     /// (whether it can have new properties added to it).
     ///

crates/js-sys/tests/wasm/Object.rs

@@ -1,5 +1,6 @@
 use wasm_bindgen::prelude::*;
 use wasm_bindgen_test::*;
+use std::f64::NAN;
 use js_sys::*;
 
 #[wasm_bindgen]
@@ -48,6 +49,25 @@ fn to_string() {
     assert_eq!(foo_42().to_string(), "[object Object]");
 }
 
+#[wasm_bindgen_test]
+fn is() {
+    let object = JsValue::from(Object::new());
+    assert!(Object::is(&object, &object));
+    assert!(Object::is(&JsValue::undefined(), &JsValue::undefined()));
+    assert!(Object::is(&JsValue::null(), &JsValue::null()));
+    assert!(Object::is(&JsValue::TRUE, &JsValue::TRUE));
+    assert!(Object::is(&JsValue::FALSE, &JsValue::FALSE));
+    assert!(Object::is(&"foo".into(), &"foo".into()));
+    assert!(Object::is(&JsValue::from(42), &JsValue::from(42)));
+    assert!(Object::is(&JsValue::from(NAN), &JsValue::from(NAN)));
+
+    let another_object = JsValue::from(Object::new());
+    assert!(!Object::is(&object, &another_object));
+    assert!(!Object::is(&JsValue::TRUE, &JsValue::FALSE));
+    assert!(!Object::is(&"foo".into(), &"bar".into()));
+    assert!(!Object::is(&JsValue::from(23), &JsValue::from(42)));
+}
+
 #[wasm_bindgen_test]
 fn is_extensible() {
     let object = Object::new();