js: Add bindings to Object.keys

src/js.rs

@@ -293,6 +293,13 @@ extern {
     #[wasm_bindgen(method, js_name = isPrototypeOf)]
     pub fn is_prototype_of(this: &Object, value: &JsValue) -> bool;
 
+    /// The Object.keys() method returns an array of a given object's property
+    /// names, in the same order as we get with a normal loop.
+    ///
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys
+    #[wasm_bindgen(static_method_of = Object)]
+    pub fn keys(object: &Object) -> Array;
+
     /// The Object constructor creates an object wrapper.
     ///
     /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object

tests/all/js_globals/Object.rs

@@ -123,6 +123,33 @@ fn is_prototype_of() {
         .test()
 }
 
+#[test]
+fn keys() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(proc_macro, wasm_custom_section)]
+
+            extern crate wasm_bindgen;
+            use wasm_bindgen::prelude::*;
+            use wasm_bindgen::js;
+
+            #[wasm_bindgen]
+            pub fn keys(obj: &js::Object) -> js::Array {
+                js::Object::keys(obj)
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                const obj = { a: 1, b: 2, c: 3 };
+                assert.deepStrictEqual(wasm.keys(obj), ["a", "b", "c"]);
+            }
+        "#)
+        .test()
+}
+
 #[test]
 fn property_is_enumerable() {
     project()