hof-y123/index.js

A collection of handy Higher-Order Functions (HOFs) for JavaScript arrays to simplify common tasks.

// 1. Sum of elements
const sum = arr => arr.reduce((acc, val) => acc + val, 0);

// 2. Average of elements
const average = arr => arr.length === 0 ? 0 : sum(arr) / arr.length;

// 3. Remove duplicates
const unique = arr => [...new Set(arr)];

// 4. Find max
const max = arr => Math.max(...arr);

// 5. Find min
const min = arr => Math.min(...arr);

// 6. Group by a function (e.g. by type or even/odd)
const groupBy = (arr, fn) =>
  arr.reduce((acc, val) => {
    const key = fn(val);
    (acc[key] = acc[key] || []).push(val);
    return acc;
  }, {});

// 7. Count frequency of elements
const frequency = arr =>
  arr.reduce((acc, val) => {
    acc[val] = (acc[val] || 0) + 1;
    return acc;
  }, {});

// 8. Shuffle array
const shuffle = arr =>
  [...arr].sort(() => Math.random() - 0.5);

// 9. Chunk into parts
const chunk = (arr, size) =>
  Array.from({ length: Math.ceil(arr.length / size) }, (_, i) =>
    arr.slice(i * size, i * size + size)
  );

// 10. Flatten nested array
const flatten = arr => arr.reduce((acc, val) => acc.concat(Array.isArray(val) ? flatten(val) : val), []);


// Export all
module.exports = {
  sum,
  average,
  unique,
  max,
  min,
  groupBy,
  frequency,
  shuffle,
  chunk,
  flatten,
};