Redux - How to add entry to array in reducer - reactjs

Question

I stuck with this bit and I can't progress - I guess solution is simple but I can't figure out. I'm trying to add entry in reducer so data in in would look something this:
state = {
entryId: {
entryName: ["something", "something2", "something3" /* and so on... */]
}
};
So far this is the closest I get, but, instead of adding new unique entry, it is replacing the one that is stored already. Also I need to be able to add this item to empty state where entryId, entryName doesn't exist yet to avoid error:
switch(type) {
case ADD_ENTRY:
return {
...state,
[entryId]: {
...state[entryId],
[entryName]: {
[uniqueEntry]: true
}
}
};
}
Any idea what I'm doing wrong?

Answer 1

If you're trying to add an element to the end of the entryName array you should be doing:
return {
...state,
[entryId]: {
...state[entryId],
[entryName]: [
...state[entryId][entryName],
uniqueEntry
]
}
};
ES6 spread with arrays works like this:
const array1 = [1, 2, 3];
const array2 = [4, 5, 6];
const eight = 8;
const newArray = ['stuff', ...array1, 'things', ...array2, ...[7, eight], 9];
console.log(newArray); // ["stuff", 1, 2, 3, "things", 4, 5, 6, 7, 8, 9]
Check out this gist which has an example of something very similar to what you're doing.
I found this set of examples extremely helpful as well. A lot of great stuff in here:
https://github.com/sebmarkbage/ecmascript-rest-spread
Update:
If entryName is initialized to undefined like you say in your comment, you could do this:
return {
...state,
[entryId]: {
...state[entryId],
[entryName]: [
...state[entryId][entryName] || [],
uniqueEntry
]
}
};
I think this is a pretty great example of how painful it can be working with React/redux using a heavily nested data structure. FWIW, it's been recommended to me many times to flatten your state as much as possible.