Bug 839979 - Implement Object.is. r=jorendorff

js/src/builtin/Object.cpp

@@ -791,6 +791,20 @@ obj_keys(JSContext *cx, unsigned argc, Value *vp)
     return true;
 }
 
+/* ES6 draft 15.2.3.16 */
+static JSBool
+obj_is(JSContext *cx, unsigned argc, Value *vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    bool same;
+    if (!SameValue(cx, args.get(0), args.get(1), &same))
+        return false;
+
+    args.rval().setBoolean(same);
+    return true;
+}
+
 static JSBool
 obj_getOwnPropertyNames(JSContext *cx, unsigned argc, Value *vp)
 {
@@ -982,6 +996,7 @@ JSFunctionSpec js::object_static_methods[] = {
     JS_FN("getPrototypeOf",            obj_getPrototypeOf,          1,0),
     JS_FN("getOwnPropertyDescriptor",  obj_getOwnPropertyDescriptor,2,0),
     JS_FN("keys",                      obj_keys,                    1,0),
+    JS_FN("is",                        obj_is,                      2,0),
     JS_FN("defineProperty",            obj_defineProperty,          3,0),
     JS_FN("defineProperties",          obj_defineProperties,        2,0),
     JS_FN("create",                    obj_create,                  2,0),

js/src/jit-test/tests/basic/object-is.js

@@ -0,0 +1,41 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ */
+
+var list = [
+    [1, 1, true],
+    [0, 1, false],
+    [3.5, 3.5, true],
+    [0, 0, true],
+    [0, -0, false],
+    [-0, 0, false],
+    [-0, -0, true],
+
+    [true, true, true],
+    [true, false, false],
+    [false, false, true],
+
+    [NaN, NaN, true],
+    [NaN, undefined, false],
+    [Infinity, -Infinity, false],
+    [Infinity, Infinity, true],
+]
+
+for (var test of list) {
+    assertEq(Object.is(test[0], test[1]), test[2])
+}
+
+var obj = {}
+assertEq(Object.is(obj, obj), true);
+assertEq(Object.is(obj, {}), false);
+assertEq(Object.is([], []), false);
+
+assertEq(Object.is(null, null, null), true);
+
+/* Not defined parameters are undefined ... */
+assertEq(Object.is(null), false);
+assertEq(Object.is(undefined), true);
+assertEq(Object.is(), true);
+
+assertEq(Object.is.length, 2);