Tag Archives: JavaScript

Check Permissions in JavaScript Client Object Model

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I had a need to check the rights a user had on a particular item in SharePoint. Unfortunately, this had to be done entirely client side. Naturally, I turned to the client object model – but it took a little time to figure out.

I wanted to query for a particular item, some (though not all) of it’s properties, and I wanted to get it’s permissions. This post by Henrik Andersson gave me a good clue, though it didn’t explicitly mention getting the properties. To get the item, with it’s properties and it’s permissions:

//var clientContext = new SP.ClientContext(.... ;
clientContext.load(listItem, 'EffectiveBasePermissions', 'ID', 'Title', 'Owner', 'Active', 'Modified', 'Editor');
clientContext.executeQueryAsync(Function.createDelegate(this, this.OnItemQueryCompleted), Function.createDelegate(this, this.OnItemQueryFailed));

That performs the query to get the item and permissions – but how do you check them? Well, you need to to use the SP.ListItem.get_effectiveBasePermissions() method. (Note: there are SP.List.get_effectiveBasePermissions() and SP.Web.get_effectiveBasePermissions() methods too, for those tiers of the hierarchy).

function OnItemQueryCompleted(sender, args) {
	var perms = listItem.get_effectiveBasePermissions();

	if (perms.has(SP.PermissionKind.editListItems)) {
	      // ....
	}
}

The permissions are retrieved into an SP.BasePermissions object, which has the .has() method that you can use to check the permissions (returns true if the user does have that permission). The Permissions mask is defined by the values in the SP.PermissionKind enumeration.

Handle Exceptions in Client Object Model callbacks

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A note to myself, of something I found on MSDN – for the ‘failed’ function on an asynchronous JavaScript call in the SharePoint Client Object Model:

function OnItemQueryFailed(sender, args)
{
   alert('Error:\n' + args.get_message() + '\n' + args.get_stackTrace());
}

Note that these details are from the SP.ClientRequestFailedEventArgs class. There are other properties too.

Error: ‘b’ is null or not an object

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This error has caused me so much pain when trying to use SharePoint’s JavaScript client-side object model (CSOM), so, in case I have it again:

  1. Check that the function exists.
  2. Check that the function is named correctly.
  3. Make sure that you’re not using “this” in the call to createDelegate, as detailed here.
    • Right: Function.createDelegate(this, onSuccessMethod)
    • Wrong: Function.createDelegate(this, this.onSuccessMethod)

    I don’t know why this difference should cause this error, but I’ve proved it true.

If you know of other causes of this error, let me know, I’ll add it to the list. I love the experience of debugging JavaScript…

Use jQuery to populate and hide fields in an EditForm.aspx

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We’ve got an interesting requirement. We’re using a SharePoint list to store documents which are related to K2 SmartObjects. One of my colleagues is building a custom user control that’s going to show information from this SmartObjects, and associated documents. We want to allow users to

  • click to add a document to our smart object entity
  • upload a file to a library
  • fill in some details
  • automatically associate that file by a GUID

Sounds complicated? Actually, it’s not so hard! Continue reading →

Get query string parameters with Regular Expressions (in JavaScript)!

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I’ve said it before, but not quite so explicitly – it’s easiest to get query string parameters with a regular expression. I keep seeing big JavaScript functions looping through and splitting the parameters up, and that might be fine if you want to store those and use them repeatedly – but if not, regexes are your friend.

This function will the value of a parameter. If the parameter requested isn’t in the query string, it returns null.If the parameter doesn’t have a value (e.g. debug in ...&debug&...) it returns an empty string.

function GetQueryParam(parameter){
var p = escape(unescape(parameter));
var regex = new RegExp("[?&]" + p + "(?:=([^&]*))?","i");
var match = regex.exec(window.location.search);
var value = null;
if( match != null ){
value = match[1];
}
return value;
}

What is MSOLayouts_MakeInvisibleIfEmpty()

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I was looking through the code of SharePoint’s Blank Web Part page layout, and I kept finding elements called _invisibleIfEmpty. Now, I’d noticed that some page layouts, such as the Splash page layout had borders on their web part zones which were only shown if the zone contained a web part. I was interested in how this might work. People keep asking for web parts with borders, preferrably ones with rounded corners. Continue reading →