Best way to update nested array using immutability-hepler

Question

I'm using immutability-helper to update state, in React. I used to update things like this:

const newElement = update(element, {
            x: {
              $apply: function(x) {
                return x * width;
              }
            },
            markers: {
              $set: element.markers
            }
          });

But what about updating a property, which is an array. Let's say markers is an array, if I create the newElement by using $set, it justs create a reference copy, hence, this:

newElement.markers[0].text = "sample"

will modify state. What would be the proper way to do that, other than this:

 const newMarkers = [];
          newElement.markers.forEach(marker => {
            const updatedMarkers = update(marker, {
              x: {
                $apply: function(x) {
                  return x * width;
                }
              },
              y: {
                $apply: function(x) {
                  return x * height;
                }
              }
            });
            newMarkers.push(updatedMarkers);
          });
newElement["markers"] = newMarkers;