Don't accept the magic

I practice a discipline when I’m reading code called “Don’t accept the magic”. Don’t accept the magic means that even if you think you understand what the output of a line of code should be, if you don’t understand how the code makes the output, you can’t accept the magic.

As a result, yesterday I spent about a half hour disecting what the Redux utility combineReducers does. Watch this video by Dan Abramov to understand what I’m talking about. The video goes fast, and explains this lovely bit of code:

function combineReducers(reducers){
  return (state = {}, action) => {
    return Object.keys(reducers).reduce(
      (nextState, key)=>{
        nextState[key] = reducers[key](state[key], action);
        return nextState
      }, {}
    )
  }
}

It’s a complex bit of work that turns multiple Redux reducers that work on slices of state into a single Redux reducer that works on the entire Redux state. There’s very little in it that is individually complex, but as a whole, it is complex. Despite the time it took me to analyze it, I’m glad I did. Every time I refuse to accept the magic, I come away with strengthened knowledge of development patterns.