indexBy

Creates an object from an array, using a function to map each value to a key.

  • Use Array.prototype.reduce() to create an object from arr.
  • Apply fn to each value of arr to produce a key and add the key-value pair to the object.
const indexBy = (arr, fn) =>
  arr.reduce((obj, v, i) => {
    obj[fn(v, i, arr)] = v;
    return obj;
  }, {});
Examples;
indexBy(
  [
    { id: 10, name: "apple" },
    { id: 20, name: "orange" },
  ],
  (x) => x.id
);
// { '10': { id: 10, name: 'apple' }, '20': { id: 20, name: 'orange' } }
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