SharePoint Online - Check If A User Is In A Group With JSOM

A few days ago, I was working in JSOM (JavaScript object model) on SharePoint Online. As per my business requirement, I have to check whether or not a user is a member of a particulate SP Group or not.

A few days ago, I was working on JSOM (JavaScript object model) on SharePoint Online. As per the business requirement, I had to check if he/she is a member of a particular SP Group or not. In that scenario, I used the following code.

Steps to use the code

To use the code, this function can be added to the targeted code file or to use in a SharePoint custom list forms or in a page. Adding to the Script Editor web part or Content Editor web part will be a good choice.

The following function named "IsGroupMember" is the function which returns a boolean value with True/False. And this function gets three parameters - the name of the Group, the user from whom we want to check, and the ClientContext. Also, it is important to mention that with groupName variable, a string value as the group visual name needs to be sent and with cUser variable, SPUser's user name needs to be sent.

Code Snippet

function IsGroupMember(groupName, cUser, clientContext) {
    var deferred = $.Deferred();
    var currentWeb = clientContext.get_web();

    var allGroups = currentWeb.get_siteGroups();
    clientContext.load(allGroups);

    var group = allGroups.getByName(groupName);
    clientContext.load(group);

    var groupUsers = group.get_users();
    clientContext.load(groupUsers);

    clientContext.executeQueryAsync(
       function onQuerySucceeded(sender, args) {
         var isUserInGroup = false;
         var groupUserEnumerator = groupUsers.getEnumerator();
         while (groupUserEnumerator.moveNext()) {
            var groupUser = groupUserEnumerator.get_current();
            if (groupUser.get_id() == cUser.get_id()) {
               isUserInGroup = true;
               break;
            }
         }
         deferred.resolve(isUserInGroup);
      },
      function onQueryFailed(sender, args) {
        console.log('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace());
        deferred.resolve(false);
         //if the funtion got ay error, it will return false.
      }
    );
    return deferred.promise();
}

Notes
In this code snippet, deferred - promise is used to increase the usability. This can be ignored if the developer wants to simply return the value or can use onComplete function.