Provide methods to define ES5 getters and setters

To allow jsdom to run in environments that don't support `__defineGetter__` and
`__defineSetter__`, implement equivalents in terms of ES5's
`Object.defineProperty`.

lib/jsdom/utils.js

@@ -39,3 +39,43 @@ exports.toFileUrl = function (fileName) {
 
   return 'file://' + pathname;
 };
+
+/**
+ * Define a setter on an object
+ *
+ * This method replaces any existing setter but leaves getters in place.
+ *
+ * - `object` {Object} the object to define the setter on
+ * - `property` {String} the name of the setter
+ * - `setterFn` {Function} the setter
+ */
+exports.defineSetter = function defineSetter(object, property, setterFn) {
+  var descriptor = Object.getOwnPropertyDescriptor(object, property) || {
+    configurable: true,
+    enumerable: true
+  };
+
+  descriptor.set = setterFn;
+
+  Object.defineProperty(object, property, descriptor);
+};
+
+/**
+ * Define a getter on an object
+ *
+ * This method replaces any existing getter but leaves setters in place.
+ *
+ * - `object` {Object} the object to define the getter on
+ * - `property` {String} the name of the getter
+ * - `getterFn` {Function} the getter
+ */
+exports.defineGetter = function defineGetter(object, property, getterFn) {
+  var descriptor = Object.getOwnPropertyDescriptor(object, property) || {
+    configurable: true,
+    enumerable: true
+  };
+
+  descriptor.get = getterFn;
+
+  Object.defineProperty(object, property, descriptor);
+};

test/jsdom/utils.js

@@ -0,0 +1,119 @@
+"use strict";
+
+var utils = require("../../lib/jsdom/utils");
+
+exports["defineSetter defines a setter"] = function (t) {
+  var o = {};
+  var called = false;
+  var expected = 'bar';
+  var actual;
+
+  utils.defineSetter(o, 'foo', function (val) {
+    called = true;
+    actual = val;
+  });
+
+  o.foo = expected;
+  t.equal(called, true);
+  t.equal(actual, expected);
+
+  t.done();
+};
+
+exports["defineSetter replaces existing setters"] = function (t) {
+  var o = {};
+  var originalCalled = false;
+  var newCalled = false;
+
+  utils.defineSetter(o, 'foo', function (val) {
+    originalCalled = true;
+  });
+
+  utils.defineSetter(o, 'foo', function (val) {
+    newCalled = true;
+  });
+
+  o.foo = true;
+  t.equal(originalCalled, false);
+  t.equal(newCalled, true);
+
+  t.done();
+};
+
+exports["defineSetter does not remove existing getters"] = function (t) {
+  var o = {};
+  var called = false;
+  var expected = 'bar';
+  var actual;
+
+  utils.defineGetter(o, 'foo', function () {
+    called = true;
+    return expected;
+  });
+
+  utils.defineSetter(o, 'foo', function (val) { /* NOP */ });
+
+  actual = o.foo;
+  t.equal(called, true);
+  t.equal(actual, expected);
+
+  t.done();
+};
+
+exports["defineGetter defines a getter"] = function (t) {
+  var o = {};
+  var called = false;
+  var expected = 'bar';
+  var actual;
+
+  utils.defineGetter(o, 'foo', function () {
+    called = true;
+    return expected
+  });
+
+  actual = o.foo;
+  t.equal(called, true);
+  t.equal(actual, expected);
+
+  t.done();
+};
+
+exports["defineGetter replaces existing getters"] = function (t) {
+  var o = {};
+  var originalCalled = false;
+  var newCalled = false;
+
+  utils.defineGetter(o, 'foo', function (val) {
+    originalCalled = true;
+  });
+
+  utils.defineGetter(o, 'foo', function (val) {
+    newCalled = true;
+  });
+
+  var actual = o.foo;
+  t.equal(originalCalled, false);
+  t.equal(newCalled, true);
+
+  t.done();
+};
+
+exports["defineGetter does not remove existing setters"] = function (t) {
+  var o = {};
+  var called = false;
+  var expected = 'bar';
+  var actual;
+
+  utils.defineSetter(o, 'foo', function (val) {
+    called = true;
+    actual = val;
+  });
+
+  utils.defineGetter(o, 'foo', function () { /* NOP */ });
+
+  o.foo = expected;
+  t.equal(called, true);
+  t.equal(actual, expected);
+
+  t.done();
+};

test/runner

@@ -94,6 +94,7 @@ var files = [
   "jsdom/index.js",
   "jsdom/parsing.js",
   "jsdom/env.js",
+  "jsdom/utils.js",
   "jsonp/jsonp.js",
   "browser/css.js",
   "browser/index.js"