AngularJS的学习--TodoMVC的分析
最近一段时间一直在看AngularJS，趁着一点时间总结一下。
先推荐几个教程
1. AngularJS入门教程 比较基础，是官方Tutorial的翻译。
2. 七步从AngularJS菜鸟到专家 也比较基础，制作了一个在线音乐播放网站。
3. AngularJS开发指南 这个教程比较全面，但我感觉翻译的有些晦涩难懂。
看过这些教程后，觉得AngularJS也懂一点了，就想用它干点事，就分析一下AngularJS写的todomvc吧。
Todomvc官网地址：http://todomvc.com/
项目的目录如下：
bower_components里放了两个文件夹，其中angular文件夹是用来一如angular.js文件的，todomvc-common文件夹里的放入了所有todo项目统一的css\js(只是用来生成左侧内容的，与项目无关)和图片。
js文件夹是大头，里面放了相应的controller(控制器)\directive(指令)\service(服务)和app.js。
test文件夹里放的是测试用的代码，不分析。
index.html是项目的view页面。
先来看一下app.js
/*global angular */ /*jshint unused:false */ 'use strict'; /** * The main TodoMVC app module * * @type {angular.Module} */ var todomvc = angular.module('todomvc', []);
就是定义了一个模块todomvc
再看一下services下的todoStorage.js
/*global todomvc */ 'use strict'; /** * Services that persists and retrieves TODOs from localStorage */ todomvc.factory('todoStorage', function () { // todos JSON字符串存储的唯一标识 var STORAGE_ID = 'todos-angularjs'; return { // 从localStorage中取出todos，并解析成JSON对象 get: function () { return JSON.parse(localStorage.getItem(STORAGE_ID) || '[]'); }, // 将todos对象转化成JSON字符串，并存入localStorage put: function (todos) { localStorage.setItem(STORAGE_ID, JSON.stringify(todos)); } }; });
使用factory方法创建了todoStorage的service方法，这个service方法的本质就是返回了两个方法get和put，两者都是用了JSON2和HTML5的特性。get将todos的内容从localStorage中取出，并解析成JSON，put将todos转化成JSON字符串，并存储到localStorage中。
再看一下directives下面的两个指令文件。
todoFocus.js
/*global todomvc */ 'use strict'; /** * Directive that places focus on the element it is applied to when the expression it binds to evaluates to true */ todomvc.directive('todoFocus', function todoFocus($timeout) { return function (scope, elem, attrs) { // 为todoFocus属性的值添加监听 scope.$watch(attrs.todoFocus, function (newVal) { if (newVal) { $timeout(function () { elem[0].focus(); }, 0, false); } }); }; });
返回function的参数中，elem就是包含该指令的元素的数组，attrs是元素的所有属性、属性名等组成的对象。
其中用到了两个AngularJS的方法
$watch(watchExpression, listener, objectEquality) 注册一个侦听器回调，每当watchExpression变化时，监听回调将被执行。
$timeout(fn[, delay][, invokeApply]) 当timeout的值达到时，执行fn函数。
todoFocus.js创建了todoFocus指令。当一个元素拥有todoFocus属性时，该指令会为该元素的todoFocus属性的值添加监听，如果todoFocus属性的值改变成true，就会执行$timeout(function () {elem[0].focus();}, 0, false);其中的延迟时间为0秒，所以会立即执行elem[0].focus()。
todoEscape.js
/*global todomvc */ 'use strict'; /** * Directive that executes an expression when the element it is applied to gets * an `escape` keydown event. */ todomvc.directive('todoEscape', function () { var ESCAPE_KEY = 27; return function (scope, elem, attrs) { elem.bind('keydown', function (event) { if (event.keyCode === ESCAPE_KEY) { scope.$apply(attrs.todoEscape); } }); }; });
todoEscape.js创建了todoEscape指令。当按下Escape键时，执行attrs.todoEscape的表达式。
看一下大头，controllers文件夹中的todoCtrl.js，这个文件略长，我就直接写注释了。
/*global todomvc, angular */ 'use strict'; /** * The main controller for the app. The controller: * - retrieves and persists the model via the todoStorage service * - exposes the model to the template and provides event handlers */ todomvc.controller('TodoCtrl', function TodoCtrl($scope, $location, todoStorage, filterFilter) { // 从localStorage中获取todos var todos = $scope.todos = todoStorage.get(); // 记录新的todo $scope.newTodo = ''; // 记录编辑过的todo $scope.editedTodo = null; // 当todos的值改变时执行其中的方法 $scope.$watch('todos', function (newValue, oldValue) { // 获取未完成的todos的数目 $scope.remainingCount = filterFilter(todos, { completed: false }).length; // 获取已完成的todos的数目 $scope.completedCount = todos.length - $scope.remainingCount; // 当且仅当$scope.remainingCount为0时，$scope.allChecked为true $scope.allChecked = !$scope.remainingCount; // 当todos的新值和旧值不相等时，向localStorage中存入todos if (newValue !== oldValue) { // This prevents unneeded calls to the local storage todoStorage.put(todos); } }, true); if ($location.path() === '') { // 如果$location.path()为空，就设置为/ $location.path('/'); } $scope.location = $location; // 当location.path()的值改变时执行其中的方法 $scope.$watch('location.path()', function (path) { // 获取状态的过滤器 // 如果path为'/active'，过滤器为{ completed: false } // 如果path为'/completed'，过滤器为{ completed: true } // 否则，过滤器为null $scope.statusFilter = (path === '/active') ? { completed: false } : (path === '/completed') ? { completed: true } : null; }); // 添加一个新的todo $scope.addTodo = function () { var newTodo = $scope.newTodo.trim(); if (!newTodo.length) { return; } // 向todos里添加一个todo，completed属性默认为false todos.push({ title: newTodo, completed: false }); // 置空 $scope.newTodo = ''; }; // 编辑一个todo $scope.editTodo = function (todo) { $scope.editedTodo = todo; // Clone the original todo to restore it on demand. // 保存编辑前的todo，为恢复编辑前做准备 $scope.originalTodo = angular.extend({}, todo); }; // 编辑todo完成 $scope.doneEditing = function (todo) { // 置空 $scope.editedTodo = null; todo.title = todo.title.trim(); if (!todo.title) { // 如果todo的title为空，则移除该todo $scope.removeTodo(todo); } }; // 恢复编辑前的todo $scope.revertEditing = function (todo) { todos[todos.indexOf(todo)] = $scope.originalTodo; $scope.doneEditing($scope.originalTodo); }; // 移除todo $scope.removeTodo = function (todo) { todos.splice(todos.indexOf(todo), 1); }; // 清除已完成的todos $scope.clearCompletedTodos = function () { $scope.todos = todos = todos.filter(function (val) { return !val.completed; }); }; // 标记所有的todo的状态（true或false） $scope.markAll = function (completed) { todos.forEach(function (todo) { todo.completed = completed; }); }; });
最后看一下index.html，这个文件我们一段一段的分析。
<!doctype html> <html lang="en" ng-app="todomvc" data-framework="angularjs"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>AngularJS • TodoMVC</title> <link rel="stylesheet" href="bower_components/todomvc-common/base.css"> <style>[ng-cloak] { display: none; }</style> </head> <body> <section id="todoapp" ng-controller="TodoCtrl"> <header id="header"> <h1>todos</h1> <form id="todo-form" ng-submit="addTodo()"> <input id="new-todo" placeholder="What needs to be done?" ng-model="newTodo" autofocus> </form> </header> <section id="main" ng-show="todos.length" ng-cloak> <input id="toggle-all" type="checkbox" ng-model="allChecked" ng-click="markAll(allChecked)"> <label for="toggle-all">Mark all as complete</label> <ul id="todo-list"> <li ng-repeat="todo in todos | filter:statusFilter track by $index" ng-class="{completed: todo.completed, editing: todo == editedTodo}"> <div class="view"> <input class="toggle" type="checkbox" ng-model="todo.completed"> <label ng-dblclick="editTodo(todo)">{{todo.title}}</label> <button class="destroy" ng-click="removeTodo(todo)"></button> </div> <form ng-submit="doneEditing(todo)"> <input class="edit" ng-trim="false" ng-model="todo.title" todo-escape="revertEditing(todo)" ng-blur="doneEditing(todo)" todo-focus="todo == editedTodo"> </form> </li> </ul> </section> <footer id="footer" ng-show="todos.length" ng-cloak> <span id="todo-count"><strong>{{remainingCount}}</strong> <ng-pluralize count="remainingCount" when="{ one: 'item left', other: 'items left' }"></ng-pluralize> </span> <ul id="filters"> <li> <a ng-class="{selected: location.path() == '/'} " href="#/">All</a> </li> <li> <a ng-class="{selected: location.path() == '/active'}" href="#/active">Active</a> </li> <li> <a ng-class="{selected: location.path() == '/completed'}" href="#/completed">Completed</a> </li> </ul> <button id="clear-completed" ng-click="clearCompletedTodos()" ng-show="completedCount">Clear completed ({{completedCount}})</button> </footer> </section> <footer id="info"> <p>Double-click to edit a todo</p> <p>Credits: <a href="http://twitter.com/cburgdorf">Christoph Burgdorf</a>, <a href="http://ericbidelman.com">Eric Bidelman</a>, <a href="http://jacobmumm.com">Jacob Mumm</a> and <a href="http://igorminar.com">Igor Minar</a> </p> <p>Part of <a href="http://todomvc.com">TodoMVC</a></p> </footer> <script src="bower_components/todomvc-common/base.js"></script> <script src="bower_components/angular/angular.js"></script> <script src="js/app.js"></script> <script src="js/controllers/todoCtrl.js"></script> <script src="js/services/todoStorage.js"></script> <script src="js/directives/todoFocus.js"></script> <script src="js/directives/todoEscape.js"></script> </body> </html>
首先是在最下面，引入相应的JS，这个就不多说了。
<script src="bower_components/todomvc-common/base.js"></script> <script src="bower_components/angular/angular.js"></script> <script src="js/app.js"></script> <script src="js/controllers/todoCtrl.js"></script> <script src="js/services/todoStorage.js"></script> <script src="js/directives/todoFocus.js"></script> <script src="js/directives/todoEscape.js"></script>
定义style[ng-cloak]，含有ng-cloak属性则不可见。
<style>[ng-cloak] { display: none; }</style>
来看添加todo的html，绑定的model为newTodo，submit的方法是todoCtrl.js中的addTodo()，会添加一条todo，点击Enter，默认触发提交事件，就触发了addTodo()方法，添加了一条todo到todos中。
<form id="todo-form" ng-submit="addTodo()"> <input id="new-todo" placeholder="What needs to be done?" ng-model="newTodo" autofocus> </form>
再看展示todos的html
<section id="main" ng-show="todos.length" ng-cloak> <input id="toggle-all" type="checkbox" ng-model="allChecked" ng-click="markAll(allChecked)"> <label for="toggle-all">Mark all as complete</label> <ul id="todo-list"> <li ng-repeat="todo in todos | filter:statusFilter track by $index" ng-class="{completed: todo.completed, editing: todo == editedTodo}"> <div class="view"> <input class="toggle" type="checkbox" ng-model="todo.completed"> <label ng-dblclick="editTodo(todo)">{{todo.title}}</label> <button class="destroy" ng-click="removeTodo(todo)"></button> </div> <form ng-submit="doneEditing(todo)"> <input class="edit" ng-trim="false" ng-model="todo.title" todo-escape="revertEditing(todo)" ng-blur="doneEditing(todo)" todo-focus="todo == editedTodo"> </form> </li> </ul> </section>
section使用ngShow方法根据todos的长度判断是否显示，加上ng-cloak属性是为了在刚开始时不要显示出AngularJS未处理的页面。可以去掉刷新试一试。
其中id为toggle-all的checkbox绑定到allChecked model上，点击触发markAll(allChecked)，将allChecked的值传入，标记所有的todos。
使用ngRepeat循环产生li标签，todo in todos | filter:statusFilter track by $index，循环todos，用statusFilter过滤，用$index追踪。ngClass绑定了两个class，{completed: todo.completed, editing: todo == editedTodo}，如果todo.completed为true，添加completed class，如果todo==editedTodo，则添加editing class。class为toggle的checkbox绑定到todo.completed。todo标题展示的label绑定了双击事件，双击触发editTodo(todo)，editTodo会将todo赋给editedTodo，然后会触发下面form中的todoFocus指令，这时候form中的input可见。按Esc就触发revertEditing(todo)，恢复到编辑前，按Enter或者失去焦点就触发doneEditing(todo) ，保存编辑后的todo。class为destroy的button绑定了click事件，点击触发removeTodo(todo)，删除掉该条todo。
最后看todos的统计信息展示的html
<footer id="footer" ng-show="todos.length" ng-cloak> <span id="todo-count"><strong>{{remainingCount}}</strong> <ng-pluralize count="remainingCount" when="{ one: 'item left', other: 'items left' }"></ng-pluralize> </span> <ul id="filters"> <li> <a ng-class="{selected: location.path() == '/'} " href="#/">All</a> </li> <li> <a ng-class="{selected: location.path() == '/active'}" href="#/active">Active</a> </li> <li> <a ng-class="{selected: location.path() == '/completed'}" href="#/completed">Completed</a> </li> </ul> <button id="clear-completed" ng-click="clearCompletedTodos()" ng-show="completedCount">Clear completed ({{completedCount}})</button> </footer>
ng-pluralize标签实现了当remainingCount个数为1时，显示 item left，否则显示 items left。
id为filters的ul标签中根据location.path()的内容不同，标记不同的a标签被选中。
id为clear-completed的button添加了点击事件，触发clearCompletedTodos()，清除掉所有已完成的todo。
分析到此结束，如有错误，或者有不明白的地方，请留言~~
