To update if exists or add new element to array of objects with JavaScript, we can check if the index of the item that matches our condition exists.

For instance, we write

const upsert = (array, element) => {
  const i = array.findIndex((_element) => _element.id === element.id);
  if (i > -1) {
    array[i] = element;
  } else {
    array.push(element);
  }
};

const array = [
  { id: 0, name: "Apple", description: "fruit" },
  { id: 1, name: "Banana", description: "fruit" },
  { id: 2, name: "Tomato", description: "vegetable" },
];

upsert(array, { id: 2, name: "Tomato", description: "fruit" });

to define the upsert function.

In it, we call array.findIndex to find the element in arraythat matches theid` value.

If it exists, then i is bigger than -1 and we assign the element to that index.

Otherwise, we call push to append element as the last item.