Implement a compactObject function

Apr 01, 2024

compactObject is a utility function which can take nested objects and arrays and remove any falsy values from them.

The values false, null, '', undefined, 0 and NaN are considered falsy.

1. Basic implementation

Do not mutate the original array. Consider only JSON serializable values will be passed to input.

function compactObject(input) {
  // other values
  if (typeof input !== 'object' && input && input != null) {
    return input;
  }

  // for arrays
  if (Array.isArray(input)) {
    const outArr = [];
    input.forEach((item) => {
      if (item) {
        outArr.push(compactObject(item));
      }
    });
    return outArr;
  }

  // for objects
  const outObj = {};
  for (const key in input) {
    // Avoid iteration of inherited keys
    if (Object.hasOwn(input, key)) {
      const value = input[key];

      // only when truthy
      if (value) {
        if (typeof value !== 'object') {
          outObj[key] = value;
        } else {
          outObj[key] = compactObject(value);
        }
      }
    }
  }

  return outObj;
}

const input = [0, 1, NaN, null, '', false, [{ name: 'John Doe', age: null, messages: ['Hi', ''] }]];

const output = compactObject(input);

/**
 * Yields:
 * [
    1,
    [
        {
            "name": "John Doe",
            "messages": [
                "Hi"
            ]
        }
    ]
]
 */
console.log(output);