Merge pull request #322 from belfz/expose-bindings/object-seal

implements Object.seal() binding

src/js.rs

@@ -431,6 +431,14 @@ extern {
     #[wasm_bindgen(method, js_name = propertyIsEnumerable)]
     pub fn property_is_enumerable(this: &Object, property: &JsValue) -> bool;
 
+    /// The Object.seal() method seals an object, preventing new properties
+    /// from being added to it and marking all existing properties as non-configurable.
+    /// Values of present properties can still be changed as long as they are writable.
+    /// 
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/seal
+    #[wasm_bindgen(static_method_of = Object)]
+    pub fn seal(value: &JsValue) -> JsValue;
+
     /// The toLocaleString() method returns a string representing the object.
     /// This method is meant to be overridden by derived objects for
     /// locale-specific purposes.

tests/all/js_globals/Object.rs

@@ -185,6 +185,57 @@ fn property_is_enumerable() {
         .test()
 }
 
+#[test]
+fn seal() {
+    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 seal(value: &JsValue) -> JsValue {
+                js::Object::seal(&value)
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                const object: any = { foo: 'bar' };
+                const sealedObject = wasm.seal(object);
+                assert.strictEqual(object, sealedObject);
+                assert.throws(() => {
+                    'use strict';
+                    sealedObject.bar = 'foo';
+                }, TypeError);
+                assert.throws(() => {
+                    'use strict';
+                    delete sealedObject.foo;
+                }, TypeError);
+
+                const primitive = 42;
+                assert.doesNotThrow(() => {
+                    'use strict';
+                    // according to ES2015, this should not throw anymore
+                    // see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/seal#Notes
+                    wasm.seal(primitive);
+                });
+
+                const array = [1, 2, 3];
+                const sealedArray = wasm.seal(array);
+                assert.throws(() => {
+                    'use strict';
+                    sealedArray.push(42);
+                }, TypeError);
+            }
+        "#)
+        .test()
+}
+
 #[test]
 fn to_locale_string() {
     project()