[英]How to keep script in partial view from loading more than once and causing errors when partial is used more than once in the same page
在 ASP.NET MVC 中工作,我创建了一个在同一页面上呈现 2 次的局部视图。 我的问题是JavaScript 包含的次数与部分视图一样多,并且 JavaScript 不喜欢重新定义类。
我的问题是:如何在部分视图中包含 JavaScript 以使其保持模块化,但仅在页面中包含一次? 我对需要将 .js 文件与部分视图的内容分开包含的解决方案不感兴趣,例如
<script src="some.js"></script>
@Html.Partial("some/partial.cshtml")
@Html.Partial("some/partial.cshtml")
但我可以接受包含在局部视图中的单独的.js 文件。 局部视图应包含使其工作所需的一切。
我的代码结构如下:
<div id=@ViewBag.id></div>
<script>
class MyClass{
constructor(divName){
this._divId = divId;
}
doSomething(){
/* do stuff with element that has id of divId */
}
}
</script>
然后,在调用文件中,我有
<body>
@Html.Partial("/Views/MyPartial.cshtml", new ViewDataDictionary() { { "id", "id_1"} })
@Html.Partial("/Views/MyPartial.cshtml", new ViewDataDictionary() { { "id", "id_2"} })
</body>
<script>
$().ready(function(){
id1Functionality = new MyClass("id_1"); // please forgive the poor naming :-)
id2Functionality = new MyClass("id_2");
id1Functionality.doSomething();
id2Functionality.doSomething();
})
</script>
一种解决方案是实现 Html 辅助扩展 function ,它只会加载一次脚本。 见下文。 (这也适用于 CSS 和其他包含的文件)。
为每个 HttpContext 实现 HtmlHelper class 和私有支持 class 的扩展作为 singleton。
public static class YourHtmlHelperExtensionClass
{
private class TagSrcAttrTracker
{
private TagSrcAttrTracker() { }
public Dictionary<string, string> sources { get; } = new Dictionary<string, string>();
public static TagSrcAttrTrackerInstance {
get {
IDictionary items = HttpContext.Current.Items;
const string instanceName = "YourClassInstanceNameMakeSureItIsUniqueInThisDictionary";
if(!items.Contains(instanceName))
items[instanceName] = new TagSrcAttrTracker();
return items[instanceName] as TagSrcAttrTracker;
}
}
}
public static MvcHtmlString IncludeScriptOnlyOnce(this HtmlHelper helper, string urlOfScript)
{
if(TagSrcAttrTracker.Instance.sources.ContainsKey(urlOfScript))
return null;
TagSrcAttrTracker.Instance.sources[urlOfScript] = urlOfScript;
TagBuilder script = new TagBuilder("script");
scriptTag.MergeAttribute("src", urlOfScript);
return MvcHtmlString.Create(script.ToString());
}
}
然后,将 JavaScript 和其他代码分离到单独的文件中。
Example.js 文件内容
class MyClass{
myFunction() {
constructor(divId){
this._divId = divId
}
doSomething() {
// do something with a div with id == divId
}
}
}
Example.cshtml 部分视图的文件内容
<link rel="stylesheet" type="text/css" href="~/Content/CustomCSS/MyPartialView.css"/>
<div id="@ViewBag.id">
Some content! Yay!
</div>
@Html.IncludeScriptOnlyOnce("/Scripts/CustomScripts/MyPartialView.js")
使用局部视图的 Example.cshtml 文件
...
<body>
<h1>Here is some content!</h1>
@Html.Partial("/Views/MyPartial.cshtml", new ViewDataDictionary() { { "id", "id_1"} })
@Html.Partial("/Views/MyPartial.cshtml", new ViewDataDictionary() { { "id", "id_2"} })
@Html.Partial("/Views/MyPartial.cshtml", new ViewDataDictionary() { { "id", "id_3"} })
</body>
<script>
$().ready(
const id1Functionality = new MyClass("id_1") // forgive the poor naming :-)
const id2Functionality = new MyClass("id_3")
const id3Functionality = new MyClass("id_2")
id1Functionality.doSomething();
id2Functionality.doSomething();
id3Functionality.doSomething();
)
</script>
部分视图可能被多次包含,并且 JavaScript 与部分视图一起打包,但 .js 文件仅包含在页面中一次,因此浏览器不会抱怨 MyClass 被多次声明。
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