长度是集合的属性。它用于计算集合包含的模型数量。
用法:
collection.length
让我们举个例子。
看这个例子:
<!DOCTYPE html>
<head>
<title>Length Collection Example</title>
<script src="https://code.jquery.com/jquery-2.1.3.min.js" type="text/javascript"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js" type="text/javascript"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js" type="text/javascript"></script>
</head>
<body>
<script type="text/javascript">
//'Cities' is a model and contains defualt value for the model
var Cities = Backbone.Model.extend({
defaults:{
city:"Hyderabad"
}
});
//'CityCollection' is an instance of the collection
var CityCollection = Backbone.Collection.extend({
model:Cities //model 'Cities' is specified by using model property
});
//The add() method adds the models 'city1', 'city2' and 'city3' to the collection instance 'mycollection'
var city1 = new Cities({city:"Banglore"});
var city2 = new Cities({city:"Delhi"});
var city3 = new Cities({city:"Mumbai"});
var mycollection = new CityCollection();
mycollection.add([city1,city2,city3]);
document.write('Number of models in collection:' + mycollection.length);
</script>
</body>
</html>
输出:
将上述代码保存在 length.html 文件中,然后在新浏览器中打开该文件。

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注:本文由纯净天空筛选整理自 Backbone.js collection.length()。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。