code: function ensureArrayAndPush(object, key, value) {
              if (!Array.isArray(object[key])) {
                  object[key] = [];
              }
              object[key].push(value);
          }
docs: Ensure that an array exists at [key] on `object`, and add `value` to it.
  
  @param {Object} object the object to mutate
  @param {string} key the object's key
  @param {*} value the value to add
  @returns {void}
  @private