ctx.exec

app.js

app.factory('ctx', function () {
  return function () {
    var ctx = SP.ClientContext.get_current();

    ctx.exec = (function () {
      var q;
      return function () {
        if (!q) {
          q = $q.when().then(function () {
            return $q(function (resolve, reject) {
              ctx.executeQueryAsync(resolve, reject);
            }).then(function () {
              q = null;
            });
          });
        }
        return q;
      };
    })();
  };
});