Getting list length from caml query

I am currently trying to determine the length of a list that is located on my SharePoint site. I am using a Caml query to retrieve the items in my list, but I can not figure out how to get the length of the result. I am using the Client Object Model and javascript / Ajax / jquery etc...

var context = new SP.ClientContext.get_current();
    var query = new SP.CamlQuery();
    var currentweb = context.get_web();

    query.set_viewXml('<View>' +
                                '<Query>'+
                                    '<Where>'+
                                        '<IsNotNull>' +
                                            '<FieldRef Name="ID" />'+
                                        '</IsNotNull>' +
                                    '</Where>'+
                                '</Query>'+
                                '<ViewFields>'+
                                    '<FieldRef Name="Name"/>'+
                                '</ViewFields>'+
                            '</View>');


    var colList= currentweb.get_lists().getByTitle("MyList");

    this.docList= colList.getItems(query);
    context.load(this.docList);
    context.ExecuteQuery();

When the code runs context.ExecuteQuery() the console prints out this.

context.ExecuteQuery is not a function