React - Improve performance by 6x

 - 2x: The unminified version contains invariants that shouldn't be used in production and slow it down.

 - 3x: Adding a shouldComponentUpdate override in order to short-cut re-rendering the component when props and state didn't change. In order to do that, we need to avoid doing mutations by doing a shallow copy and only modifying what changed

 - When React 0.5.0 will be released, it will give another 1.5x.

Other miscellaneous changes:

 - Update class="..." to className="..." to work in 0.5.0 (still works in 0.4.1)
 - Use prop="..." instead of prop='...'
 - Use filter(f, this) instead of filter(f.bind(this)) to prevent a function allocaton

labs/architecture-examples/react/index.html

@@ -12,7 +12,7 @@
 		<div id="benchmark"></div>
 
 		<script src="bower_components/todomvc-common/base.js"></script>
-		<script src="bower_components/react/react.js"></script>
+		<script src="bower_components/react/react.min.js"></script>
 		<script src="bower_components/react/JSXTransformer.js"></script>
 		<script src="bower_components/director/build/director.min.js"></script>
 

labs/architecture-examples/react/js/app.jsx

@@ -43,17 +43,15 @@
 			}
 
 			var val = this.refs.newField.getDOMNode().value.trim();
-			var todos;
 			var newTodo;
 
 			if (val) {
-				todos = this.state.todos;
 				newTodo = {
 					id: Utils.uuid(),
 					title: val,
 					completed: false
 				};
-				this.setState({todos: todos.concat([newTodo])});
+				this.setState({todos: this.state.todos.concat([newTodo])});
 				this.refs.newField.getDOMNode().value = '';
 			}
 
@@ -63,16 +61,22 @@
 		toggleAll: function (event) {
 			var checked = event.target.checked;
 
-			this.state.todos.forEach(function (todo) {
-				todo.completed = checked;
+			var newTodos = this.state.todos.map(function (todo) {
+				return Utils.extend({}, todo, {completed: checked});
 			});
 
-			this.setState({todos: this.state.todos});
+			this.setState({todos: newTodos});
 		},
 
 		toggle: function (todo) {
-			todo.completed = !todo.completed;
-			this.setState({todos: this.state.todos});
+			var newTodos = this.state.todos.map(function (t) {
+				if (t !== todo) {
+					return t;
+				}
+				return Utils.extend({}, t, {completed: !todo.completed});
+			});
+
+			this.setState({todos: newTodos});
 		},
 
 		destroy: function (todo) {
@@ -92,8 +96,14 @@
 		},
 
 		save: function (todo, text) {
-			todo.title = text;
-			this.setState({todos: this.state.todos, editing: null});
+			var newTodos = this.state.todos.map(function (t) {
+				if (t !== todo) {
+					return t;
+				}
+				return Utils.extend({}, t, {title: text});
+			});
+
+			this.setState({todos: newTodos, editing: null});
 		},
 
 		cancel: function () {
@@ -115,9 +125,6 @@
 		render: function () {
 			var footer = null;
 			var main = null;
-			var todoItems = {};
-			var activeTodoCount;
-			var completedCount;
 
 			var shownTodos = this.state.todos.filter(function (todo) {
 				switch (this.state.nowShowing) {
@@ -128,11 +135,12 @@
 				default:
 					return true;
 				}
-			}.bind(this));
+			}, this);
 
-			shownTodos.forEach(function (todo) {
-				todoItems[todo.id] = (
+			var todoItems = shownTodos.map(function (todo) {
+				return (
 					<TodoItem
+						key={todo.id}
 						todo={todo}
 						onToggle={this.toggle.bind(this, todo)}
 						onDestroy={this.destroy.bind(this, todo)}
@@ -142,13 +150,13 @@
 						onCancel={this.cancel}
 					/>
 				);
-			}.bind(this));
+			}, this);
 
-			activeTodoCount = this.state.todos.filter(function (todo) {
+			var activeTodoCount = this.state.todos.filter(function (todo) {
 				return !todo.completed;
 			}).length;
 
-			completedCount = this.state.todos.length - activeTodoCount;
+			var completedCount = this.state.todos.length - activeTodoCount;
 
 			if (activeTodoCount || completedCount) {
 				footer =

labs/architecture-examples/react/js/todoItem.jsx

@@ -23,6 +23,7 @@
 			}
 			return false;
 		},
+
 		handleEdit: function () {
 			// react optimizes renders by batching them. This means you can't call
 			// parent's `onEdit` (which in this case triggeres a re-render), and
@@ -33,6 +34,7 @@
 				node.focus();
 				node.setSelectionRange(node.value.length, node.value.length);
 			}.bind(this));
+			this.setState({editText: this.props.todo.title});
 		},
 
 		handleKeyDown: function (event) {
@@ -41,8 +43,6 @@
 				this.props.onCancel();
 			} else if (event.keyCode === ENTER_KEY) {
 				this.handleSubmit();
-			} else {
-				this.setState({editText: event.target.value});
 			}
 		},
 
@@ -54,21 +54,24 @@
 			return {editText: this.props.todo.title};
 		},
 
-		componentWillReceiveProps: function (nextProps) {
-			if (nextProps.todo.title !== this.props.todo.title) {
-				this.setState(this.getInitialState());
-			}
+		shouldComponentUpdate: function (nextProps, nextState) {
+			return (
+				nextProps.todo.id !== this.props.todo.id ||
+				nextProps.todo !== this.props.todo ||
+				nextProps.editing !== this.props.editing ||
+				nextState.editText !== this.state.editText
+			);
 		},
 
 		render: function () {
 			return (
-				<li class={Utils.stringifyObjKeys({
+				<li className={Utils.stringifyObjKeys({
 					completed: this.props.todo.completed,
 					editing: this.props.editing
 				})}>
-					<div class="view">
+					<div className="view">
 						<input
-							class="toggle"
+							className="toggle"
 							type="checkbox"
 							checked={this.props.todo.completed ? 'checked' : null}
 							onChange={this.props.onToggle}
@@ -76,11 +79,11 @@
 						<label onDoubleClick={this.handleEdit}>
 							{this.props.todo.title}
 						</label>
-						<button class='destroy' onClick={this.props.onDestroy} />
+						<button className="destroy" onClick={this.props.onDestroy} />
 					</div>
 					<input
 						ref="editField"
-						class="edit"
+						className="edit"
 						value={this.state.editText}
 						onBlur={this.handleSubmit}
 						onChange={this.handleChange}

labs/architecture-examples/react/js/utils.jsx

@@ -32,6 +32,19 @@
 			return (store && JSON.parse(store)) || [];
 		},
 
+		extend: function () {
+			var newObj = {};
+			for (var i = 0; i < arguments.length; i++) {
+				var obj = arguments[i];
+				for (var key in obj) {
+					if (obj.hasOwnProperty(key)) {
+						newObj[key] = obj[key];
+					}
+				}
+			}
+			return newObj;
+		},
+
 		stringifyObjKeys: function (obj) {
 			var s = '';
 			var key;