SharePoint 2013 get user groups by CSOM

Question

I wrote some code to get the current user groups by CSOM.

function getCurrentUser() {
    this.clientContext = new SP.ClientContext.get_current();
    this.oWeb = clientContext.get_web();
    currentUser = this.oWeb.get_currentUser();
    this.clientContext.load(currentUser);
    clientContext.load(allGroups);
    this.clientContext.executeQueryAsync(Function.createDelegate(this, this.onQuerySucceededUser), Function.createDelegate(this, this.onQueryFailedUser));
}
function onQuerySucceededUser() {
    //debugger;
    var groups = currentUser.get_groups();
    var groupsEnum = groups.getEnumerator();
    while (groupsEnum.moveNext()) {
        //handle group
    }
}

But I get this error:

The collection has not been initialized. It has not been requested or the request has not been executed. It may need to be explicitly requested.

on this line: groups.getEnumerator();
How can I solve it?

Answer 1

Move this line

var groups = currentUser.get_groups();

To your getCurrentUser method and make sure to load it

this.clientContext.load(groups);

before executing the request, this way you will have it loaded in your success-function

Answer 2

The code should look like this:

    function getCurrentUser() {
        this.clientContext = new SP.ClientContext.get_current();
        this.oWeb = clientContext.get_web();
        currentUser = this.oWeb.get_currentUser();
        this.allGroups = currentUser.get_groups();    
        clientContext.load(allGroups);
        this.clientContext.executeQueryAsync(Function.createDelegate(this, this.onQuerySucceededUser), Function.createDelegate(this, this.onQueryFailedUser));
    }
    function onQuerySucceededUser() {
        var groupsEnum = allGroups.getEnumerator();
        while (groupsEnum.moveNext()) {

        //handle group
        var group = groupsEnum.get_current();
        }
    }