freeCodeCamp Challenge Guide: Remove an Item from an Array

Guide
1

Remove an Item from an Array

Solutions

Solution 1 (Click to Show/Hide) 
const immutableReducer = (state = [0, 1, 2, 3, 4, 5], action) => {
  switch (action.type) {
    case "REMOVE_ITEM":
      // don't mutate state here or the tests will fail
      return [
        ...state.slice(0, action.index),
        ...state.slice(action.index + 1, state.length)
      ];
    // or return state.slice(0, action.index).concat(state.slice(action.index + 1, state.length));
    default:
      return state;
  }
};

const removeItem = index => {
  return {
    type: "REMOVE_ITEM",
    index
  };
};

const store = Redux.createStore(immutableReducer);

Code Explanation

  • array.slice(fromIndex, untilIndex) returns a new array
  • 1st slice from the first item’s index (0 inclusive) until indexToRemove(action.index exclusive)
  • 2nd slice from item right after indexToRemove (action.index + 1 inclusive) until length (last item’s index + 1 exclusive)
  • since slice returns a new array, combine both parts with […array1, …array2] spread operator
  • or combine them with .concat()
Solution 2 (Click to Show/Hide) 
const immutableReducer = (state = [0, 1, 2, 3, 4, 5], action) => {
  switch (action.type) {
    case 'REMOVE_ITEM':
      // Don't mutate state here or the tests will fail
      return state.filter((_, index) => index !== action.index);
    default:
      return state;
  }
};

const removeItem = (index) => {
  return {
    type: 'REMOVE_ITEM',
    index
  }
}

const store = Redux.createStore(immutableReducer);

Code Explanation

Using the index on the action and the index from Array.prototype.filter() to filter out the element.

30 Likes