javascript - How to delete an array in redux

Question

This is the initial content in my redux. Now I need to click on a list, for example, click on test 2, and I will delete the list. When I first enter, the content in the status is like this. My judgment in redux is like this, but the result is that the parameters are gone, but the position of the array is still there...

我想大声告诉你 · Answer

return state.arr.filter(item => item.id !== id);

欧阳克 · Answer

If you perform a map operation like this on any array, it will happen, leaving an array with holes. . .
The correct approach is

let newState = state.slice()
newState.splice(2, 1)
return newState

Every time you operate on the redux state, try to return a new object, such as

return Object.assign({}, oldState, newState)
return [...oldState, ...newState] // or [...oldState].concat(newState)

Looks like this...

The other thing is, if the empty position in your map does not specify a return value, then the default value returned is undefined. Why does it become null...