React 上的 JS 扩展运算符工作流程

Question

React suggests not to mutate state. I have an array of objects which I am manipulating based on some events. My question is, is it okay to write it like this:

const makeCopy = (arr) => arr.map((item) => ({ ...item }));

function SomeComponenet() {
    const [filters, setFilters] = useState(aemFilterData);

    const handleFilterClick = (filter, c) => {
        let copiedFilters = makeCopy(filters);

        /**
         * Apply toggle on the parent as well
         */
        if (!("parentId" in filter)) {
            copiedFilters[filter.id].open = !copiedFilters[filter.id].open;
        }
        setFilters(copiedFilters);
    }
}

Am I mutating the original object by doing like above? Or does it make a difference if written like this:

const makeCopy = (arr) => arr.map((item) => ({ ...item }));

function SomeComponent() {
    const [filters, setFilters] = useState(aemFilterData);

    const handleFilterClick = (filter, c) => {
        let copiedFilters = makeCopy(filters);

        /**
         * Apply toggle on the parent as well
         */
        if (!("parentId" in filter)) {
            copiedFilters = copiedFilters.map((f) => {
            if (filter.id === f.id) {
              return {
                ...f,
                open: !f.open,
              };
            } else {
              return { ...f };
            }
          });
        }
        setFilters(copiedFilters);
    }
}

What's the preferred way to do this? Spread operators are getting a lot verbose and I am not liking it, but I prefer it if that's how I need to do it here. immutable.js and immer or not an option right now.

Answer 1

The first approach is mutating on the original object reference because you're not creating a deep clone.

copiedFilters[filter.id].open = !copiedFilters[filter.id].open;

Here reference of copiedFilters[filter.id] and filters[filter.id] is same.

Although this may work, the second approach is more correct since that way you create a new object reference when you use spread operator. With this approach open will be the updated value in copiedFilters but filters should still have the old value.

You can create a deep clone when you copy but that would be waste of computation and memory, I don't think it's needed here.