IE8 compatibility

Author: goto-bus-stop

events.js

@@ -19,8 +19,17 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
+var objectCreate = Object.create || objectCreatePolyfill
+var objectKeys = Object.keys || objectKeysPolyfill
+var bind = Function.prototype.bind || functionBindPolyfill
+
 function EventEmitter() {
-  EventEmitter.init.call(this);
+  if (!this._events || !Object.prototype.hasOwnProperty.call(this, '_events')) {
+    this._events = objectCreate(null);
+    this._eventsCount = 0;
+  }
+
+  this._maxListeners = this._maxListeners || undefined;
 }
 module.exports = EventEmitter;
 
@@ -34,28 +43,29 @@ EventEmitter.prototype._maxListeners = undefined;
 // added to it. This is a useful default which helps finding memory leaks.
 var defaultMaxListeners = 10;
 
-Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
-  enumerable: true,
-  get: function() {
-    return defaultMaxListeners;
-  },
-  set: function(arg) {
-    // check whether the input is a positive number (whose value is zero or
-    // greater and not a NaN).
-    if (typeof arg !== 'number' || arg < 0 || arg !== arg)
-      throw new TypeError('"defaultMaxListeners" must be a positive number');
-    defaultMaxListeners = arg;
-  }
-});
-
-EventEmitter.init = function() {
-  if (!this._events || this._events === Object.getPrototypeOf(this)._events) {
-    this._events = Object.create(null);
-    this._eventsCount = 0;
-  }
-
-  this._maxListeners = this._maxListeners || undefined;
-};
+var hasDefineProperty;
+try {
+  var o = {};
+  if (Object.defineProperty) Object.defineProperty(o, 'x', { value: 0 });
+  hasDefineProperty = o.x === 0;
+} catch (err) { hasDefineProperty = false }
+if (hasDefineProperty) {
+  Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
+    enumerable: true,
+    get: function() {
+      return defaultMaxListeners;
+    },
+    set: function(arg) {
+      // check whether the input is a positive number (whose value is zero or
+      // greater and not a NaN).
+      if (typeof arg !== 'number' || arg < 0 || arg !== arg)
+        throw new TypeError('"defaultMaxListeners" must be a positive number');
+      defaultMaxListeners = arg;
+    }
+  });
+} else {
+  EventEmitter.defaultMaxListeners = defaultMaxListeners;
+}
 
 // Obviously not all Emitters should be limited to 10. This function allows
 // that to be increased. Set to zero for unlimited.
@@ -200,7 +210,7 @@ function _addListener(target, type, listener, prepend) {
 
   events = target._events;
   if (!events) {
-    events = target._events = Object.create(null);
+    events = target._events = objectCreate(null);
     target._eventsCount = 0;
   } else {
     // To avoid recursion in the case that type === "newListener"! Before
@@ -247,7 +257,9 @@ function _addListener(target, type, listener, prepend) {
         w.emitter = target;
         w.type = type;
         w.count = existing.length;
-        console.warn('%s: %s', w.name, w.message);
+        if (typeof console === 'object' && console.warn) {
+          console.warn('%s: %s', w.name, w.message);
+        }
       }
     }
   }
@@ -291,7 +303,7 @@ function onceWrapper() {
 
 function _onceWrap(target, type, listener) {
   var state = { fired: false, wrapFn: undefined, target: target, type: type, listener: listener };
-  var wrapped = onceWrapper.bind(state);
+  var wrapped = bind.call(onceWrapper, state);
   wrapped.listener = listener;
   state.wrapFn = wrapped;
   return wrapped;
@@ -330,7 +342,7 @@ EventEmitter.prototype.removeListener =
 
       if (list === listener || list.listener === listener) {
         if (--this._eventsCount === 0)
-          this._events = Object.create(null);
+          this._events = objectCreate(null);
         else {
           delete events[type];
           if (events.removeListener)
@@ -376,11 +388,11 @@ EventEmitter.prototype.removeAllListeners =
       // not listening for removeListener, no need to emit
       if (!events.removeListener) {
         if (arguments.length === 0) {
-          this._events = Object.create(null);
+          this._events = objectCreate(null);
           this._eventsCount = 0;
         } else if (events[type]) {
           if (--this._eventsCount === 0)
-            this._events = Object.create(null);
+            this._events = objectCreate(null);
           else
             delete events[type];
         }
@@ -389,15 +401,15 @@ EventEmitter.prototype.removeAllListeners =
 
       // emit removeListener for all listeners on all events
       if (arguments.length === 0) {
-        var keys = Object.keys(events);
+        var keys = objectKeys(events);
         var key;
         for (i = 0; i < keys.length; ++i) {
           key = keys[i];
           if (key === 'removeListener') continue;
           this.removeAllListeners(key);
         }
         this.removeAllListeners('removeListener');
-        this._events = Object.create(null);
+        this._events = objectCreate(null);
         this._eventsCount = 0;
         return this;
       }
@@ -486,3 +498,22 @@ function unwrapListeners(arr) {
   }
   return ret;
 }
+
+function objectCreatePolyfill(proto) {
+  var F = function() {};
+  F.prototype = proto;
+  return new F;
+}
+function objectKeysPolyfill(obj) {
+  var keys = [];
+  for (var k in obj) if (Object.prototype.hasOwnProperty.call(obj, k)) {
+    keys.push(k);
+  }
+  return k;
+}
+function functionBindPolyfill(context) {
+  var fn = this;
+  return function () {
+    return fn.apply(context, arguments);
+  };
+}

package.json

@@ -23,11 +23,13 @@
     "node": ">=0.4.x"
   },
   "devDependencies": {
+    "isarray": "^2.0.2",
     "mocha": "~1.21.4",
+    "object-keys": "^1.0.11",
     "zuul": "~1.10.2"
   },
   "scripts": {
     "test": "mocha --ui qunit -- tests/index.js && zuul -- tests/index.js"
   },
   "license": "MIT"
-}
+}

tests/common.js

@@ -28,7 +28,7 @@ var mustCallChecks = [];
 function runCallChecks(exitCode) {
   if (exitCode !== 0) return;
 
-  var failed = mustCallChecks.filter(function(context) {
+  var failed = filter(mustCallChecks, function(context) {
     if ('minimum' in context) {
       context.messageSegment = 'at least ' + context.minimum;
       return context.actual < context.minimum;
@@ -38,13 +38,15 @@ function runCallChecks(exitCode) {
     }
   });
 
-  failed.forEach(function(context) {
+  for (var i = 0; i < failed.length; i++) {
+    var context = failed[i];
     console.log('Mismatched %s function calls. Expected %s, actual %d.',
         context.name,
         context.messageSegment,
         context.actual);
-    console.log(context.stack.split('\n').slice(2).join('\n'));
-  });
+    // IE8 has no .stack
+    if (context.stack) console.log(context.stack.split('\n').slice(2).join('\n'));
+  }
 
   assert.strictEqual(failed.length, 0);
 }
@@ -90,3 +92,12 @@ exports.mustNotCall = function(msg) {
     assert.fail(msg || 'function should not have been called');
   };
 };
+
+function filter(arr, fn) {
+  if (arr.filter) return arr.filter(fn);
+  var filtered = [];
+  for (var i = 0; i < arr.length; i++) {
+    if (fn(arr[i], i, arr)) filtered.push(arr[i]);
+  }
+  return filtered
+}

tests/legacy-compat.js

@@ -12,7 +12,5 @@ for (var i=0 ; i<fns.length ; ++i) {
 }
 
 if (!Array.isArray) {
-    Array.isArray = function(arr) {
-        return Object.prototype.toString.call(arr) === '[object Array]';
-    }
+    Array.isArray = require('isarray');
 }

tests/listeners-side-effects.js

@@ -23,15 +23,16 @@ require('./common');
 var assert = require('assert');
 
 var EventEmitter = require('../').EventEmitter;
+var objectKeys = require('object-keys');
 
 var e = new EventEmitter();
 var fl;  // foo listeners
 
 fl = e.listeners('foo');
 assert.ok(Array.isArray(fl));
 assert.strictEqual(fl.length, 0);
-assert.ok(!(e._events instanceof Object));
-assert.strictEqual(Object.keys(e._events).length, 0);
+if (Object.create) assert.ok(!(e._events instanceof Object));
+assert.strictEqual(objectKeys(e._events).length, 0);
 
 e.on('foo', assert.fail);
 fl = e.listeners('foo');

tests/max-listeners.js

@@ -24,6 +24,9 @@ var assert = require('assert');
 var events = require('../');
 var e = new events.EventEmitter();
 
+var hasDefineProperty = !!Object.defineProperty;
+try { Object.defineProperty({}, 'x', { value: 0 }); } catch (err) { hasDefineProperty = false }
+
 e.on('maxListeners', common.mustCall());
 
 // Should not corrupt the 'maxListeners' queue.
@@ -33,9 +36,12 @@ var throwsObjs = [NaN, -1, 'and even this'];
 var maxError = /^TypeError: "n" argument must be a positive number$/;
 var defError = /^TypeError: "defaultMaxListeners" must be a positive number$/;
 
-throwsObjs.forEach(function(obj) {
+for (var i = 0; i < throwsObjs.length; i++) {
+  var obj = throwsObjs[i];
   assert.throws(function() { e.setMaxListeners(obj); }, maxError);
-  assert.throws(function() { events.defaultMaxListeners = obj; }, defError);
-});
+  if (hasDefineProperty) {
+    assert.throws(function() { events.defaultMaxListeners = obj; }, defError);
+  }
+}
 
 e.emit('maxListeners');

tests/once.js

@@ -72,9 +72,10 @@ assert.throws(function() {
       var restArgs = args.slice(1);
       assert.ok(Array.isArray(params));
       assert.strictEqual(params.length, restArgs.length);
-      params.forEach(function(param, index) {
+      for (var index = 0; index < params.length; index++) {
+        var param = params[index];
         assert.strictEqual(param, restArgs[index]);
-      });
+      }
   	}));
 
     EventEmitter.prototype.emit.apply(ee, args);

tests/remove-all-listeners.js

@@ -36,9 +36,10 @@ function expect(expected) {
     var sortedActual = actual.sort();
     var sortedExpected = expected.sort();
     assert.strictEqual(sortedActual.length, sortedExpected.length);
-    sortedActual.forEach(function(value, index) {
+    for (var index = 0; index < sortedActual.length; index++) {
+      var value = sortedActual[index];
       assert.strictEqual(value, sortedExpected[index]);
-    });
+    }
   });
   function listener(name) {
     actual.push(name);
@@ -109,7 +110,7 @@ function expect(expected) {
   // Check for regression where removeAllListeners() throws when
   // there exists a 'removeListener' listener, but there exists
   // no listeners for the provided event type.
-  assert.doesNotThrow(ee.removeAllListeners.bind(ee, 'foo'));
+  assert.doesNotThrow(function () { ee.removeAllListeners(ee, 'foo') });
 }
 
 {

tests/set-max-listeners-side-effects.js

@@ -22,10 +22,11 @@
 require('./common');
 var assert = require('assert');
 var events = require('../');
+var objectKeys = require('object-keys');
 
 var e = new events.EventEmitter();
 
-assert.ok(!(e._events instanceof Object));
-assert.strictEqual(Object.keys(e._events).length, 0);
+if (Object.create) assert.ok(!(e._events instanceof Object));
+assert.strictEqual(objectKeys(e._events).length, 0);
 e.setMaxListeners(5);
-assert.strictEqual(Object.keys(e._events).length, 0);
+assert.strictEqual(objectKeys(e._events).length, 0);

tests/subclass.js

@@ -23,6 +23,7 @@ var common = require('./common');
 var assert = require('assert');
 var EventEmitter = require('../').EventEmitter;
 var util = require('util');
+var objectKeys = require('object-keys');
 
 var after_checks = [];
 after(function() {
@@ -53,8 +54,8 @@ assert.throws(function() {
 }, /blerg/);
 
 after_checks.push(function() {
-  assert.ok(!(myee._events instanceof Object));
-  assert.strictEqual(Object.keys(myee._events).length, 0);
+  if (Object.create) assert.ok(!(myee._events instanceof Object));
+  assert.strictEqual(objectKeys(myee._events).length, 0);
 });