Today I Learned

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Matching Multiple Values In A Switch Statement

Switch statements are a handy way to execute different branches of code based on a value match. This is often what is used in Redux reducers when updating the state in response to certain actions.

But what if you need multiple values to result in the same branch of execution without duplicating the code?

The execution of a switch statement falls through, so after one match, it will continue to try and do subsequent matches if you don’t interrupt the execution with a break or return. Conveniently, this solves our problem of matching multiple values.

switch (action.type) {
  case "UPDATE_NAME":
  case "UPDATE_DURATION":
    let newData = anotherReducer(state.data, action);
    return { ...state, data: newData };
  default:
    return state;
}

See the MDN docs for more details.