Compact object

JavaScript, Object, Array, Recursion · Nov 27, 2020

Deeply removes all falsy values from an object or array.

Use recursion.
Initialize the iterable data, using Array.isArray(), Array.prototype.filter() and Boolean for arrays in order to avoid sparse arrays.
Use Object.keys() and Array.prototype.reduce() to iterate over each key with an appropriate initial value.
Use Boolean to determine the truthiness of each key's value and add it to the accumulator if it's truthy.
Use typeof to determine if a given value is an object and call the function again to deeply compact it.

const compactObject = val => {
  const data = Array.isArray(val) ? val.filter(Boolean) : val;
  return Object.keys(data).reduce(
    (acc, key) => {
      const value = data[key];
      if (Boolean(value))
        acc[key] = typeof value === 'object' ? compactObject(value) : value;
      return acc;
    },
    Array.isArray(val) ? [] : {}
  );
};

const obj = {
  a: null,
  b: false,
  c: true,
  d: 0,
  e: 1,
  f: '',
  g: 'a',
  h: [null, false, '', true, 1, 'a'],
  i: { j: 0, k: false, l: 'a' }
};
compactObject(obj);
// { c: true, e: 1, g: 'a', h: [ true, 1, 'a' ], i: { l: 'a' } }

Compact object

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