Advantage of SharePoint Client Object Model for JavaScript
Web page can interact with SharePoint without requiring a page refresh. In the background, the page uses JavaScript to communicate with SharePoint via the COM to retrieve or update data in SharePoint.
Accessing SharePoint
The first thing to note about the COM with JavaScript is that it is disconnected from SharePoint in the sense that in order to retrieve or update data in SharePoint, asynchronous calls to the server must be made. Because of its asynchronous nature, the page can continue to be responsive to the user while the data is being retrieved or updated in the background. This can be both an asset and a liability if not handled properly.
In order to access the COM in a webpage, a reference to the JavaScript file containing the COM code must be included. There are 3 JavaScript files which contain the code for the COM: SP.js, SP.Core.js, and SP.Runtime.js. SharePoint provides the SharePoint:ScriptLink server control tag for referencing JavaScript files. Using the ScriptLink control will:
assure that the JavaScript file is loaded only once
assure that dependency files are also loaded
In a SharePoint Application page, the ScriptLink tag should be declared within the PlaceHolderAdditionalPageHead Content Placeholder.
<asp:Content ID="PageHead" ContentPlaceHolderID="PlaceHolderAdditionalPageHead" runat="server" />
<SharePoint:ScriptLink Name="SP.js" LoadAfterUI="true" runat="server" />
</asp:Content>
Web page can interact with SharePoint without requiring a page refresh. In the background, the page uses JavaScript to communicate with SharePoint via the COM to retrieve or update data in SharePoint.
Accessing SharePoint
The first thing to note about the COM with JavaScript is that it is disconnected from SharePoint in the sense that in order to retrieve or update data in SharePoint, asynchronous calls to the server must be made. Because of its asynchronous nature, the page can continue to be responsive to the user while the data is being retrieved or updated in the background. This can be both an asset and a liability if not handled properly.
In order to access the COM in a webpage, a reference to the JavaScript file containing the COM code must be included. There are 3 JavaScript files which contain the code for the COM: SP.js, SP.Core.js, and SP.Runtime.js. SharePoint provides the SharePoint:ScriptLink server control tag for referencing JavaScript files. Using the ScriptLink control will:
assure that the JavaScript file is loaded only once
assure that dependency files are also loaded
In a SharePoint Application page, the ScriptLink tag should be declared within the PlaceHolderAdditionalPageHead Content Placeholder.
<asp:Content ID="PageHead" ContentPlaceHolderID="PlaceHolderAdditionalPageHead" runat="server" />
<SharePoint:ScriptLink Name="SP.js" LoadAfterUI="true" runat="server" />
</asp:Content>
