我正在做一个 Backbone.js 应用程序的helloworld示例,只有当脚本src标记包含在主体中而不是头中时,它才能工作(我希望它们在的位置)。如果我将它们放在标头中并执行警报(el)表示未定义。但是,如果我在正文中有脚本src标记并执行alert(el)它写的是object HTMLBodyElement
,hello world的例子也能用。(这是我能让它工作的唯一方法)
为什么会这样呢?
"不起作用"
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>hello-backbonejs</title>
<link rel="stylesheet" href="static/style.css">
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.18/jquery-ui.min.js"></script>
<script src="http://ajax.cdnjs.com/ajax/libs/json2/20110223/json2.js"></script>
<script src="http://documentcloud.github.com/underscore/underscore-min.js"></script>
<script src="http://documentcloud.github.com/backbone/backbone-min.js"></script>
<script src="static/backbone.localStorage-min.js"></script>
<script src="app.js"></script>
</head>
<body>
</body>
</html>
工作
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>hello-backbonejs</title>
<link rel="stylesheet" href="static/style.css">
</head>
<body>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.18/jquery-ui.min.js"></script>
<script src="http://ajax.cdnjs.com/ajax/libs/json2/20110223/json2.js"></script>
<script src="http://documentcloud.github.com/underscore/underscore-min.js"></script>
<script src="http://documentcloud.github.com/backbone/backbone-min.js"></script>
<script src="static/backbone.localStorage-min.js"></script>
<script src="app.js"></script>
</body>
</html>
这是javascript
(function($){
// **ListView class**: Our main app view.
var ListView = Backbone.View.extend({
el: $('body'), // attaches `this.el` to an existing element.
// `initialize()`: Automatically called upon instantiation. Where you make all types of bindings, _excluding_ UI events, such as clicks, etc.
initialize: function(){
_.bindAll(this, 'render'); // fixes loss of context for 'this' within methods
this.render(); // not all views are self-rendering. This one is.
},
// `render()`: Function in charge of rendering the entire view in `this.el`. Needs to be manually called by the user.
render: function(){
$(this.el).append("<ul> <li>hello world</li> </ul>");
alert(this.el);
}
});
// **listView instance**: Instantiate main app view.
var listView = new ListView();
})(jQuery);
1条答案
按热度按时间k75qkfdt1#
执行此操作时:
当脚本被加载时,DOM中会出现一个
<body>
,特别是当你点击下面的按钮时,会出现一个<body>
:当您这样做时:
当你点击
el: $('body')
时不会有<body>
,所以你的el
在 Backbone 网解开$('body')
后将结束为undefined
。我想你搞不清楚这两者之间的区别:
和
第一个立即执行函数,第二个与
并且在DOM准备就绪时执行函数。您可能希望JavaScript看起来更像这样: