Will this be considered a pure reducer function in redux?

Question

I have this reducer function and I am incrementing the value of voteScore by 1 inside it. Is this the right way to do it without breaking the constraint that reducer function should be pure function?

function comment (state = {}, action) {
 ...
 switch(action.type) {
 ...
  case UP_VOTE_COMMENT:
   const upVoteScore = parseInt(state[id]['voteScore'], 10) + 1

   return {
    ...state,
    [id]: {
     ...state[id],
     voteScore: upVoteScore
    }
   }
 }
}

It is a pure function because it has no side effects. However, parse and increment logic might be better off in an action. — Davin Tryon, Aug 23 '17 at 19:42
Does it satisfy the definition of *pure*? Does it always produce the same output given the same input, and have no side effects? — Oliver Charlesworth, Aug 23 '17 at 19:43
Also, I have to sort the comments based on the vote score. Will sort inside one of the cases in the reducer be still ok? — limitlessriver, Aug 23 '17 at 19:55
@DavinTryon Isn't action (I am using action-creator) just supposed to return the object with **type** property? — limitlessriver, Aug 23 '17 at 20:00
@DavinTryon, limitlessriver That's a matter of style. Neither way is right and neither is wrong. — Scimonster, Aug 23 '17 at 20:02

score 2 · Accepted Answer · answered Aug 23 '17 at 19:43

2

Yes. The idea of a pure function is that it always produces the same output based on the input.

The current voteScore is part of the "input" in the parameters.

answered Aug 23 '17 at 19:43

dbuss1

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Will this be considered a pure reducer function in redux?

1 Answers1